The number of 2-digit prime numbers in which digits are also prime is:

Correct option is A

The possible numbers are: 22, 23, 25, 27, 32, 33, 35, 37, 52, 53, 55, 57, 72, 73, 75, 77.
Check for Primality:
Now, we need to check which of these numbers are prime.
22 (2 x 11) - Not prime
23 - Prime
25 (5 x 5) - Not prime
27 (3 x 9) - Not prime
32 (2 x 16) - Not prime
33 (3 x 11) - Not prime
35 (5 7) - Not prime
37 - Prime
52 (2 x 26) - Not prime
53 - Prime
55 (5 x 11) - Not prime
57 (3 x 19) - Not prime
72 (2 x 36) - Not prime
73 - Prime
75 (3 x 25) - Not prime
77 (7 x 11) - Not prime
Count the Primes:
The prime numbers are 23, 37, 53, and 73.
There are 4 such prime numbers.
Therefore, the number of 2-digit prime numbers in which digits are also prime is 4.
The answer is (a) 4.