Answer
a. Yes, b. Yes, c. No. Please see explanations below.
Work Step by Step
We need to check if the following conditions are satisfied: $np≥5$ and $nq≥5$
a. $np=10>5$ and $nq=n(1−p)=40>5$, so it can be approximated by a normal distribution.
b. $np=24>5$ and $nq=n(1−p)=6>5$, so it can be approximated by a normal distribution.
c. $np=17>5$ and $nq=n(1−p)=3<5$, so it can not be approximated by a normal distribution.