课后练习：

1. This plant life called phytoplankton is a_________resource that helps ________the worst of the "greenhouse gases" involved in global warming.

A. vital; absorbB. vital; to absorb

C. valued; absorbD. vital; absorbing

2. Whether the lost productivity of the phytoplankton is directly due to increased ocean temperatures ________ for at least the past 20 years ________part of an extremely complex puzzle"

A. that have been recorded; remain

B. that have been recorded; remains

C. that have recorded; remains

D. that have been recorded; reminds

3. Primary production of plankton in the North Pacific has decreased ________more than 9 percent during the past 20 years, and by nearly 7 percent in the North Atlantic.

A. by; byB. by; 不填C. 不填; by

4. Stanford University scientists ________ two other NASA satellites and one ________ by the Defense Department have observed dramatic new changes in the vast ice sheets along the west coast of Antarctica.

A. using; flyingB. used; flownC. using flown

5. Icebergs in Antarctica ________letters and numbers for aerial surveys across millions of square miles of the southern ocean.

A. designated byB. are designated C. are designated by

6.________, the C-19 iceberg is only the second-largest recorded in the Ross Sea region.

A. Huge as it isB. As it is huge C. As huge it is

7. The huge iceberg has been stuck against the coast ever ________it broke ________from the Ross Ice Shelf last year.

A. since; inB. since; offC. because; off

本课重点学习内容：动词短语、被动语态和定语从句，以及现在分词和过去分词作定语。