1. Simple photographic lenses can't ________ sharp, undistorted images over a wide field.
A. to form B. are formed C. forming D. form
2. Of all the factors affecting agricultural yields, weather is the one ________ the most.
A. it influences farmers B. that influences farmers
C. farmers that it influences D. why farmers influence it
3. By tracking the eye of a hurricane, forecasters can determine the speed at which ________.
A. is a storm moving B. a storm is moving
C. is moving a storm D. a moving storm
4. During the flood of 1927, the Red Cross, ________ out of emergency headquarters in
A. operates B. is operating C. has operated D. operating
5. Of all the economically important plants, palms have been ________.
A. the least studied B. study the least
C. study less and less D. to study the less
6. During an eclipse of the sun, ________ in the shadow of the Moon. joozone.com