Answer: A, B, D
The para nitro group withdraws electrons by the -M and -I effects, increasing the partial positive charge on the carbonyl carbon and making it more electrophilic. 4-Nitrobenzaldehyde therefore adds cyanide faster and has a larger hydration constant than benzaldehyde. It is also more reactive, not less reactive, than 4-methoxybenzaldehyde, whose +M group deactivates the carbonyl.