Aldol Condensation

Which of the following esters cannot undergo Claisen self-condensation?

Which of the following when heated with a dilute base gives the given product as the final product?

The final product of the above reaction and name of the reaction is 

Which of the following can be the possible product of the above reaction?

(a) 

(b)   

(c)      

Which of the following will undergo base catalysed condensation reaction with cyclopentadiene to form this compound?

The compound $\mathrm{X}$ is

${\mathrm{CCl}}_3\mathrm{CHO}$ (chloral) does not undergo aldol condensation because