Tā nà shuāng zōngsè de yǎnjīng hěn mírén.
Her brown eyes are very charming.
There are various measure words that correlate with matching nouns in Chinese. In this sentence, the Chinese measure word is “双 (shuāng)”, being normally matched with “眼睛 (yǎnjīng) eyes”, the measure word “副 (fù)” is often used to modify “眼镜 (yǎnjìng) glasses”, and the measure word “个 (gè)” can modify “眼神 (yǎnshén) emotion showing in eyes”. Hence, the correct answer is A.
Never use the measure word “副 (fù) a pair of” to describe “眼睛 (yǎnjīng) eyes”