Сложное подлежащее
1) This datum proved ... the student in solving the problem.
a. to have helped
b. to be helped
c. to be helping

2) They seem ... attentively to his speech
a. to be listened
b. to be listening
c. listen

3) The person to be interviewed is supposed ... English well
a. to speak
b. have being spoken
c. to have spoken

4) He seems ... with the documents now.
a. to be working
b. work
c. to work