Some grammars question in TOEIC exam

Hi all,

i am wondering some grammars phrase in TOEIC, i hope you can explain for me.

1.....

the answersheet is (c), but i think , it should (a-interesting) because Applicants is an active pronount

111. Applicants ---- in applying for the job openings should notify the personnel no later than 3 April and submit 2 letters of reference.

a. interesting

b. interest

c. interested

d. who interested

2......

the answersheet is (b-contact) but I don't understand

119. We have concluded that it is imperative Mr. Min ------ us by the end of week not to fail to get the contract .

a. contacts

b. contact

c. be contacted

d. has contacted

3.........

the answersheet is (b); but i think it should (a-surprising) because we need a nound

136. ------- enough to everyone , the cheaper old model was more durable, efficient and even lighter than the new model.

a. Surprising

b. Surprisingly

c. Surprised

d. Surprise

4.................

140. It is a good idea to keep the extra generators ------- in case there is an power outage.

a. operation

b. operational

c. operate

d. operatively

Thanks in advance and please explain !