Swimmers must be very strong in order to build up speed because of the high resistance of the water. Runners, ____, must struggle against the heavy resistance of the air and ground.

A. generally   B. similarly   C. naturally  D. probably

Swimmers must be very strong in order to build up speed because of the high resistance of the water. Runners, ____, must struggle against the heavy resistance of the air and ground.

A. generally   B. similarly   C. naturally  D. probably

Swimmers must be very strong in order to build up speed because of the high resistance of the water. Runners, ____, must struggle against the heavy resistance of the air and ground.

A. generally   B. similarly   C. naturally  D. probably

Swimmers must be very strong in order to build up speed because of the high resistance of the water. Runners, ____, must struggle against the heavy resistance of the air and ground.

A. generally　　 B. similarly　　 C. naturally　　 D. probably

Swimmers must be very strong in order to build up speed because of the high resistance of the water. Runners, ____, must struggle against the heavy resistance of the air and ground.

1. A.
   generally
2. B.
   similarly
3. C.
   naturally
4. D.
   probably