观察下列各式

（x-1）（x+1）=x²-1

（x-1）（x²+x+1）=x³-1

（x-1）（x³+x²+x+1）=x⁴-1

…

（1）分解因式：x⁵-1=______；

（2）根据规律可得（x-1）（x^n-1+…+x+1）=______（其中n为正整数）；

（3）计算：（3-1）（3⁵⁰+3⁴⁹+3⁴⁸+…+3²+3+1）；

（4）计算：（-2）¹⁹⁹⁹+（-2）¹⁹⁹⁸+（-2）¹⁹⁹⁷+…+（-2）³+（-2）²+（-2）+1．

— He ought ot have been warned of the danger.

— ____, but he wouldn't listen to me. [ ]

A. Yes, he ought to

B. So he was

C. So was he

D. So it was with him