1. He was the first man who left the burning building.
He was the first man to leave the burning building.
2. The couple who live in the next door are both doctors.
The couple living in the next door are both doctors.
3.the people who are waiting for the bus in the rain are getting wet.
The people waiting for the bus in the rain are getting wet.
4. The students who didn't come to class yesterday explained their absence to the teacher.
The students not coming to class yesterday explained the teacher.
5. Did you get the message which concerned the special meeting?
Dis you get the message concerning the special meeting?
Relative clauses replaced by participles and to-inf:
1. Lan is the second student who enters the classroom.
Lan is the second student to enter the classroom.
2. The psychologists who study the nature of sleep have made important discoveries.
The psychologists studying the nature of sleep have made important discoveries.
3. He was the only man who reached the top of the mountain.
He was the only man reaching the top of the mountain.