运用平方差，完全平方公式解方程：

（1）16（x-1）²=225

（2）4x²-4x+1=x²-6x+9

（3）9（x+1）²=4（x-1）²

（4）x²-4x+4=（3-2x）²

The moment I will never forget is _____ my parents discussed my new school life with me before the new term started.

A．that

B．which

C．when

D．where