—Where's____?
—It's on the bed.
A:Tom's trousers
B:Tom's pen's
C:Tom's pen
D:pen of Tom
设NA为阿伏加德罗常数的值,下列叙述正确的是
如图,在坐标系中放置一菱形OABC,已知∠ABC=60°,OA=1.先将菱形OABC沿x轴的正方向无滑动翻转,每次翻转60°,连续翻转2015次,点B的落点依次为B1,B2,B3,…,则B2015的坐标为____.
如图为青蛙的生殖发育过程图,请据图回答下列问题: