Answer
See explanation below.
Work Step by Step
a.) I- has the greater polarizability because it is the bigger ion.
b.) CH2 = CH2 has the greater polarizability because it has pi electrons while CH3βCH3 lacks them. The electron clouds of the pi electrons in CH2=CH2 can be distorted readily since they are held loosely (relative to sigma electrons).
c.) H2Se has the greater polarizability because of its larger size.