普通累犯是指被判处有期徒刑以上刑罚的犯罪分子,刑罚执行完毕或者赦免以后,在( )年以内再犯应当判处有期徒刑以上刑罚之罪的犯罪人。
A.二
B.三
C.四
D.五
参考答案:D
He was thinking about the problem when an apple fell off the tree, _____ him right on the head.[ ]
A. hit
B. having hit
C. hitting
D. and hitting
条约无效的原因有哪些?