If p

Solution:

Let the two odd prime numbers $p_{1}$ and $p_{2}$ be 5 and 3 .

Then, 

$p_{1}^{2}=5^{2}$

$=25$

And

$p_{2}^{2}=3^{2}$

= 9

Thus,

p_{1}{ }^{2}-p_{2}{ }^{2}=25-9

= 16

16 is even number.

Take another example, with $p_{1}$ and $p_{2}$ be 11 and 7 .

Then, 

$p_{1}^{2}=11^{2}$

= 121

And

$p_{2}{ }^{2}=7^{2}$

= 496

Thus,

$p_{1}{ }^{2}-p_{2}{ }^{2}=121-49$

=72

72 is even number.

Thus, we can say that $p_{1}{ }^{2}-p_{2}{ }^{2}$ is even number

In general the square of odd prime number is odd. Hence the difference of square of two prime numbers is odd 

Hence the correct choice is (a).