$32 \cdot 20$ In decimal numbers, the number of prime numbers less than 100 and with a units digit of 7 is
(A) 4.
(B) 5.
(C) 6.
(D) 7.
(E) 8.
(38th American High School Mathematics Examination, 1987)
[Solution] The prime numbers less than 100 that end with 7 are
$$
7,17,37,47,67,97 \text {. }
$$

There are 6 in total.
Therefore, the answer is $(C)$.