第二次世界大战以后，建立了以黄金为核心的布雷顿森林体系。
参考答案：错
利用光电管产生光电流的电路如图所示．电源的正极应接在______端（填“a”或“b”）；若电流表读数为8μA，则每 秒从光电管阴极发射的光电子至少是______个（已知电子电量为 l.6×10-19C）
—Why did John asked me about the problem?
—______, he tried to find a better way to settle it.
A. Not to be satisfied
B. Don't satisfy
C. Not being satisfied
D. Not satisfied
