The alkane from below having two secondary hydrogens is :

The problem asks for the alkane with exactly two secondary hydrogens. Secondary hydrogens are attached to secondary carbon atoms, which are bonded to exactly two other carbon atoms.

We will analyze each option by drawing the carbon skeleton and identifying the types of carbon atoms and their attached hydrogens.

Option A: 4-Ethyl-3,4-dimethyloctane

The parent chain is octane (8 carbons). Substituents: a methyl group at position 3, and at position 4, an ethyl group and a methyl group.

Structure:

$$ \text{C1} - \text{C2} - \text{C3} - \text{C4} - \text{C5} - \text{C6} - \text{C7} - \text{C8} $$

At C3: methyl group → C3 bonded to C2, C4, and CH₃ → tertiary carbon → one hydrogen (tertiary).

At C4: ethyl group (-CH₂CH₃) and methyl group (-CH₃) → C4 bonded to C3, C5, CH₂ (of ethyl), and CH₃ → quaternary carbon → no hydrogen.

Ethyl group: -CH₂CH₃ → the CH₂ group is secondary carbon (bonded to C4 and CH₃) → two hydrogens (secondary).

Methyl groups: all primary carbons → primary hydrogens.

Chain analysis:

C1: primary carbon → three hydrogens (primary).

C2: bonded to C1 and C3 → secondary carbon → two hydrogens (secondary).

C5: bonded to C4 and C6 → secondary carbon → two hydrogens (secondary).

C6: bonded to C5 and C7 → secondary carbon → two hydrogens (secondary).

C7: bonded to C6 and C8 → secondary carbon → two hydrogens (secondary).

C8: primary carbon → three hydrogens (primary).

Secondary hydrogens: C2 (2), C5 (2), C6 (2), C7 (2), ethyl CH₂ (2) → total 10 secondary hydrogens.

Not the required alkane.

Option B: 2,2,3,3-Tetramethylpentane

The parent chain is pentane (5 carbons). Substituents: two methyl groups at C2 and two methyl groups at C3.

Structure:

$$ \text{C1} - \text{C2} - \text{C3} - \text{C4} - \text{C5} $$

At C2: two methyl groups → C2 bonded to C1, C3, CH₃, and CH₃ → quaternary carbon → no hydrogen.

At C3: two methyl groups → C3 bonded to C2, C4, CH₃, and CH₃ → quaternary carbon → no hydrogen.

Chain analysis:

C1: bonded to C2 → primary carbon → three hydrogens (primary).

C4: bonded to C3 and C5 → secondary carbon → two hydrogens (secondary).

C5: bonded to C4 → primary carbon → three hydrogens (primary).

Methyl groups: four methyl groups (all primary carbons) → each has three primary hydrogens.

Secondary hydrogens: only from C4 → two secondary hydrogens.

This matches the requirement.

Option C: 2,2,4,5-Tetramethylheptane

The parent chain is heptane (7 carbons). Substituents: two methyl groups at C2, one methyl at C4, one methyl at C5.

Structure:

$$ \text{C1} - \text{C2} - \text{C3} - \text{C4} - \text{C5} - \text{C6} - \text{C7} $$

At C2: two methyl groups → C2 bonded to C1, C3, CH₃, and CH₃ → quaternary carbon → no hydrogen.

At C4: methyl group → C4 bonded to C3, C5, CH₃, and H → tertiary carbon → one hydrogen (tertiary).

At C5: methyl group → C5 bonded to C4, C6, CH₃, and H → tertiary carbon → one hydrogen (tertiary).

Chain analysis:

C1: primary carbon → three hydrogens (primary).

C3: bonded to C2 and C4 → secondary carbon → two hydrogens (secondary).

C6: bonded to C5 and C7 → secondary carbon → two hydrogens (secondary).

C7: primary carbon → three hydrogens (primary).

Methyl groups: four methyl groups (all primary carbons) → primary hydrogens.

Secondary hydrogens: C3 (2) and C6 (2) → total four secondary hydrogens.

Not the required alkane.

Option D: 2,2,4,4-Tetramethylhexane

The parent chain is hexane (6 carbons). Substituents: two methyl groups at C2 and two methyl groups at C4.

Structure:

$$ \text{C1} - \text{C2} - \text{C3} - \text{C4} - \text{C5} - \text{C6} $$

At C2: two methyl groups → C2 bonded to C1, C3, CH₃, and CH₃ → quaternary carbon → no hydrogen.

At C4: two methyl groups → C4 bonded to C3, C5, CH₃, and CH₃ → quaternary carbon → no hydrogen.

Chain analysis:

C1: primary carbon → three hydrogens (primary).

C3: bonded to C2 and C4 → secondary carbon → two hydrogens (secondary).

C5: bonded to C4 and C6 → secondary carbon → two hydrogens (secondary).

C6: primary carbon → three hydrogens (primary).

Methyl groups: four methyl groups (all primary carbons) → primary hydrogens.

Secondary hydrogens: C3 (2) and C5 (2) → total four secondary hydrogens.

Not the required alkane.

Only option B has exactly two secondary hydrogens.

Final Answer: B