1. (3) is will replace are
2. (2) at will replace upon
3. (1)All will replace Everyone of
4. (4) No error
5. (2)than will replace when
6. (2)comprises/is comprised of will replace comprises of will replace comprise of
7. (3)feet will replace two legs
8. (2)travelling will replace to travel
9. (3)is will replace are
10. (2)having will replace to have
