$36 \cdot 48$ In one night, the number of times the hour, minute, and second hands overlap is
(A) 2.
(B) 4.
(C) 6.
(D) 24.
(China Hubei Province Huanggang Junior High School Mathematics Competition, 1993)
[Solution] The three hands of a clock coincide if and only if it is exactly 12 o'clock. Thus, in a day and night, the hour, minute, and second hands coincide only twice.
Therefore, the answer is (A)