The vibrational spectrum of a molecule exhibits a strong line with P and R branches at a frequency $${\nu _1}$$ and a weaker line at a frequency $${\nu _2}$$ . The frequency $${\nu _3}$$ is not shown up. Its vibrational Raman spectrum shows a strongly polarized line at frequency $${\nu _3}$$ and no feature at $${\nu _1}$$ and $${\nu _2}$$ .
Which of the following statements is correct?

A. The molecule could be linear

B. The molecule lacks a centre of inversion

C. $${\nu _1}$$ arises from a symmetric stretching mode

D. $${\nu _3}$$ arises from a bending mode

Answer: Option A