Answer:
The correct answer is -
A. a, c, g
B. e, b, f & d
Explanation:
Part A- the options a, c, g are the options that show mutation or replacement by a single base change
a) Phenylalanine: UUU UUC
Leucine: UUA UUG
Only one base change
c) Alanine: Â GCU Â GCC Â GCC GCG
  Thr:     ACU ACC ACA ACG
only one base change
g) Prolin: Â CCU CCC Â CCA Â CCG
 Serine: UCU UCC UCA UCG
Part B:
All other replacements will not be consistent with the Genetic Code if single base substitutions occur in option e, b, f & d