Correct option is (a) &crarr
The best explanation: &crarr represents a downwards arrow with corner leftwards. &zeta is for greek small letter zeta, &upsih is for greek upsilon, &oelig is for latin small letter o. Number for &crarr is ↵, for &zeta is ζ, for &upsih is ϒ, for &oelig is œ.