________ Gian ________ Tara are studying Chinese history now. They find it rich and amazing.
A:Both; and
B:Not only; but also
C:Either; or
D:Neither; nor
如图所示,一根质量不计长为1m的绳子,能承受的最大拉力为14N,其一端固定于天花板上,另一端系一质量为1kg的小球,整个装置处于静止状态,现对小球施加一冲量,若要将绳子拉断,作用在球上的水平冲量至少应为多少?(g取10m/s2)
例:do——did
①am/is____ ②get____ ③buy____
④see____ ⑤learn____ ⑥decide____
⑦give____ ⑧thank____ ⑨are____