Let the probability of correct answer of B be X and the probability of correct answer of C be Y..

(1) is known as, (1-y) *1/4 =112.

xy= 1/4

X=3/8，y=2/3。

(2)P = 3/4 * 3/8 *( 1-2/3)+3/4 *( 1-3/8)* 2/3+( 1-3/4)* 3/8 * 2/3 = 7/ 16