Vegetables _____many kinds of vitamins and many other useful materials, so we must eat them______．

Effective measures should be taken to ______ the rare species _______ being over-killed by human beings.

The policeman _______ the facts again and again, but couldn’t piece them together.

In doing scientific experiments one must be _______ careful with the instruments.

Since the global financial crises , the export of Chinese goods has managed to ____ roughly, and now everything goes well in foreign trade.