1.It is a year and a half later that they _____ the famous actor _____ guilty.
A.had,declaring C.made,declared
C.made,declaring D.had,declared
Right Answer:D
2.Discovery in a South African cave suggests that modern human behavior _____ much earlier than _____
A.begin,Previously thought B.began,previously thought
C.should begin,previous thinking
D.began,previous thinking
Right Answer:B
3.He _____ spends his holidays in the moutains though occasionally he goes to the seaside instead.
A.usually B.constantly C.rarely D.always
Right Answer:A
请解释一下上面各题，谢谢！

make sb do sth 是表示强迫某人做某事的意思，这里的do不能用分词，只能用原形
这里意思是，使某人被迫声明，have sb done (使某人被迫做某事）所以用declare的过去分词形式表被动。

2.人类行为的开始比人们以前认识到的更早。这个（开始）是一个过去的动作，用
去式，句子在than后省略了主语people.人们（认识到）也是一个过去动作，而且有
previously这样的词表示以前，think就必须用过去式。

3.因为句子中的though occasionally （尽管偶尔），就排除了D.always（总是）。
如果总是怎么样，就不能在偶尔了。矛盾。
rarely和occasionally 表示的频率差不多，没有多大区别。though表示转折，它前后比较的词的频率应该相差很多。
sometimes,usually,always,rarely,never，occasionally等是非确定频率副词，
一般用来回答how often？
constantly是程度副词，一般回答to what extent?到什么程度？
例如hardly 几乎不almost几乎，都是程度副词
constantly 和occasionally不是一类副词，就是遵循前后一致原则，也不能用