Answer
(a) 4.5 V
(b) 1.5 V
Work Step by Step
(a) In a series connection, total voltage= sum of individual voltages.
$V=V_{1}+V_{2}+V_{3}=1.5\,V+1.5\,V+1.5\,V=4.5\,V$
(b) When identical batteries are connected in parallel,
Total voltage $V=V_{1}=V_{2}=V_{3}=1.5\,V$