forbid的两个过去式有什么区别

Most schools forbid chewing gum, but in a few years they might consider changing that rule. Why? Scientists are finding evidence that gum chewing may be good for your health. It may even help improve your test scores.
This exciting research is just beginning. And in the meantime, companies are also experimenting with adding vitamins, minerals, medicines, and other substances that could give gum the power to cure headaches and fight everything from serious diseases to bad breath.
Other researchers are finding that gum might work better than a pill to deliver medicines and other substances into the bloodstream. That’s because the lining (膜) of our cheeks can absorb certain substances more quickly than our stomachs and intestines (肠) can.
That discovery could help other researchers develop medicine-containing gums that fight colds, ease headaches, battle nervousness, and more. Scientists might even create antimicrobial (抗菌的) gums that cure bad breath.
Those projects may take years, but gum scientists have already had at least one recent success: They’ve created a gum that could help us stay awake.
Researchers have produced a gum called Stay Alert. Each stick has as much caffeine as a cup of coffee. It can take an hour for the caffeine in coffee to have its full effect, but the caffeine in Stay Alert hits in just a few minutes.
The gum is easy to transport and it’s stable in cold and hot climates. Unlike a pill, it doesn’t require water to swallow. Those qualities make it easy for soldiers to use.
For now, Stay Alert is available only to the military (军队). The manufacturer may one day offer it for sale to the public. People who work at night, such as truck drivers and medical personnel who ride in ambulances, might benefit from a product like Stay Alert.
小题1: The passage mainly talks about _____.

A．the rule of forbidding chewing gum in school

B．new research on chewing gum

C．different kinds of chewing gum

D．the relationship between chewing gum and medicine

小题2: What does the underlined word “hits” in Paragraph 6 probably mean?

A．Touches.

B．Attacks.

C．Takes effect.

D．Affects badly.

小题3:According to the passage, Stay Alert is a gum which can help people _____.

A．stay awake	B．fight colds
C．cure headaches	D．overcome nervousness

小题4: It can be inferred from the passage that _____.

A．stay Alert is not easy to store

B．stay Alert needs water to swallow

C．stay Alert is available to the public now

D．we can’t buy gums that cure bad breath now