In this case, since carbon is in group IVA, it has four valence electrons so it needs four bonds to attain the octet. However, as carbon and bromine are bonded, carbon needs four bromines as each bromine provides only one electron for them to attain the octet as bormine has seven valence electrons for which it is in group VIIA. Therefore, the Lewis structure showing the four bonds and the seven free electrons of each bromine is B.
