When astronauts return to the earth's atmosphere, helicopters fly to________they would land, ready to collect them.

When astronauts return to the earth's atmosphere, helicopters fly to________they would land, ready to collect them.

1. A.
   what
2. B.
   where
3. C.
   which
4. D.
   that

 When astronauts return to the earth's atmosphere, helicopters fly to________they would land, ready to collect them.

A. what              B. where                   C. which                      D. that

When astronauts return to the earth's atmosphere, helicopters fly to          they would land, ready to collect them.

A．what            B．where           C．which          D．that

When astronauts return to the earth’s atmosphere, helicopters fly to________they would land, ready to collect them.