Select the correct indirect form of the given sentence.
Bhola said to his friend, "How can I make this charcoal white?"

A

Bhola asked his friend how can I make this charcoal white.

B

Bhola asked his friend how could he make that charcoal white.

C

Bhola asked his friend how he could make that charcoal white.

D

Bhola told his friend how he could make that charcoal white.