Total number of nucleophiles from the following is :
$$NH_{3},PhSH,(H_{3}C)_{2}S,H_{2}C=CH_{2},\ominus\\O H,H_{3}O^{\oplus},(CH_{3})_{2}CO,\rightleftharpoons NCH_{3}$$

A nucleophile is a species that can donate a pair of electrons to an electrophilic centre. We examine each species in turn.

$$NH_3$$ (ammonia): Nitrogen carries a lone pair of electrons, making it a well-known nucleophile. ✓

$$PhSH$$ (thiophenol): Sulfur has two lone pairs and is large and polarisable, making thiophenol a strong nucleophile. ✓

$$(H_3C)_2S$$ (dimethyl sulfide): The sulfur atom has two lone pairs readily available for donation. ✓

$$H_2C{=}CH_2$$ (ethylene): While the $$\pi$$-bond can participate in electrophilic addition, ethylene lacks a lone pair on a specific atom. In the JEE convention it is not counted as a nucleophile. ✗

$${}^{\ominus}OH$$ (hydroxide ion): Carries a full negative charge and lone pairs on oxygen. One of the strongest common nucleophiles. ✓

$$H_3O^{\oplus}$$ (hydronium ion): Positively charged and electron-deficient; it is an acid/electrophile, not a nucleophile. ✗

$$(CH_3)_2CO$$ (acetone): Although the carbonyl oxygen has lone pairs, acetone is classified as an electrophile at its carbonyl carbon and is not counted as a nucleophile in this context. ✗

$$:C{=}NCH_3$$ (methyl isocyanide, $$CH_3NC$$): In an isocyanide the terminal carbon bears a lone pair, making it an excellent nucleophile (this property is exploited in the carbylamine reaction). ✓

The five nucleophiles are therefore: $$NH_3,\; PhSH,\; (H_3C)_2S,\; {}^{\ominus}OH,\; CH_3NC$$.

Hence, the correct answer is Option D (5).