To be effective, recognition and rewards systems should have the following characteristics EXCEPT:

A:There should be clear criteria for rewards and a planned system for their us B:Recognition and rewards should be based on activities and performance under a person's contro C:Recognition and rewards should consider cultural difference D:Make the required performance unachievable for most team member to ensure that all team members strive for excellence throughout the projec

I should not have laughed if I ________ you were serious.

A:thought B:would think C:had thought D:have thought

Humans have altered the world’s climate by (1) heat-trapping gases since almost the beginning of civilization and even prevented the start of an ice age several thousand years ago, a scientist said.
Most scientists (2) a rise (3) global temperatures over the past century (4) to emissions of carbon dioxide (5) human activities like driving cars and operating factories.
Dr. William Ruddiman, a professor at the University of Virginia, said at a meeting of the American Geophysical Union (6) humans’ effect (7) climate went back nearly 10, 000 years (8) people gave up hunting and gathering and began farming.
In a commentary accompanying the article, Dr. Thomas J. Crowley of Duke University, said he (9) Dr. Ruddiman’s premise at first. "But when I started reading, Dr. Crowley wrote, "I could not help but (10) whether he just might be (11) something."
The climate of the last 10,000 years has been unusually stable, (12) civilization to flourish. But that is only because people chopped down swaths of forest in Europe, China and India for croplands and pastures. Carbon dioxide (13) by the destruction of the forests, plus methane, another heat-trapping gas, (14) by irrigated rice fields in Southeast Asia, trapped enough heat to (15) an expected natural cooling.
Levels of carbon dioxide and methane rise and fall in natural cycles (16) thousands of years, and both reached a peak at the end of the last ice age 11 ;000 years ago. Both then declined (17) expected.
Both (18) declining through the present day, leading to lower temperatures, and a new ice age should have begun 4,000 to 5,000 years ago, Dr. Ruddiman said. Instead, levels of carbon dioxide reversed 8,000 wears ago. The decline (19) methane levels reversed 5,000 years ago, (20) with the advent of irrigation rice farming.

A:have been B:would have been C:could have been D:should have

l should very much like to have gone to that party of theirs, but______.

A:I'm not invited B:I have not been invited C:I was not invited D:I will not be invited

I should very much like to have gone to that party of theirs, but ______.

A:I'm not invited B:I have not been invited C:I was not invited D:I will not be invited

l should very much like to have gone to that party of theirs, but（）

A:I'm not invited B:I have not been invited C:I was not invited D:I will not be invited

l should very much like to have gone to that party of theirs, but______.

A:I'm not invited B:I have not been invited C:I was not invited D:I will not be invited