看看这俩英语选择题1.The chair looks rather hard,but in fact it is ver

看看这俩英语选择题
1.The chair looks rather hard,but in fact it is very comfortable to ___.A.sit B.sit on C.be seat D.be sat on
2.The girl refused to____ ,though she had the hope of winning the first prize in the contest.A,take part B.join it C...
第一个选B,第2个选A 为什么第一个要带上介词,而第2个不带?
我知道take part后面省略了in the contest
其实，sit on后面也省略了the chair 为什么take part in the contest省略成take part而sit on the chair省略成sit on
3楼的朋友，take part也是相当于一个不及物动词,并且，这和及物不及物没什么关系，不及物后面不跟宾语就是了 不定式为不及物动词，必须有必要的介词？i want to fly.难道是病句？