题目内容：

A single 10-second kiss can transfer as many as 80 million bacteria, according to Dutch scientists.

They monitored the kissing behavior of 21 couples and found those who kissed nine times a day were most likely to share salivary bugs (唾液细菌).

Studies suggest the mouth is home to more than 700 different types of bacteria – but the report reveals some are exchanged more easily than others.

The research is published in the journal Microbiome (微生物组). A team from the Netherlands Organization for Applied Scientific Research (TNO) asked the couples a series of questions to assess their kissing habits, including how frequently they had kissed in the last year and when they last locked lips.

Scientists took bacterial samples from the volunteers’ tongues and saliva before and after a strictly timed 10-second kiss. One member of the couples then drank a probiotic (益生菌) drink, containing an easily identifiable mixture of bugs. On the couple’s second kiss, scientists were able to detect the volume of bacteria transferred to the other partner – on average 80 million bacteria in a single 10-second kiss.  But while bacteria in the saliva seemed to change quickly in response to a kiss, bug populations on the tongue remained more stable.

Prof Remco Kort, who led the research, said: “French kissing is a great example of exposure to a gigantic（巨大的）number of bacteria in a short time.”

“These types of investigations may help us design future bacterial therapies and help people with troublesome bacterial problems.”

A growing number or researchers are looking at the microbiome – an ecosystem of some 100 trillion micro-organisms that live in and on our bodies. Scientists say these populations may be essential for health and the prevention of disease.

1.According to the passage, bacteia can be exchanged during a kiss through     .

A. saliva       B. tongues        C. lips       D. breath

2.Why did the scientists have one of the couples drink a probiotic drink?

A. Because they want to observe the response of their bodies.

B. Because they intend to protect the bacteria in the couples’ mouths,

C. Because they want to detect the volume of the transferred bacteria.

D. Because they want to keep a balanced environment in the couples’ bodies.

3.What’s the purpose of the research?

A. To guide healthy kiss.

B. To limit the times of kissing.

C. To avoid kissing different people.

D. To help design future bacteria therapies.

4.We can learn from the passage that        .

A. French kissing should be advocated

B. we need to lock lips when kissing if we love her / him

C. the exchanged bacteria through kissing do great harm to the other

D. some of the microbiome may be essential for health though exchanged during a kiss