国债是国家为实现其职能，而以国家信用为基础所举借的债务，它是( )的重要手段。

Scientists are trying to find a link between pollution and ______.

A．intelligence levels

B．antisocial behavior

C．birth defects

D．divorce percentage

Scientists are trying to find a link between pollution and ______.

A．intelligence levels

B．antisocial behavior

C．birth defects

D．divorce percentage

Scientists are trying to find a link between pollution and ______.

A．intelligence levels

B．antisocial behavior

C．birth defects

D．divorce percentage

The scientists are trying to find oust if masks may or may not______. A. overuse face masks

B. deal with the mask problem seriously

C. rub their faces and noses in the subway

D. protest against the mask guidelines

E. help protect people from being attacked by a flu F. announce the results of their mask research

The scientists are trying to find oust if masks may or may not______.

根据下列短文，回答 27～30 题。

第 27 题 The scientists are trying to find out if masks may or may not ________.

A lot of cities are trying new ways to treat garbage mainly because ______.

A．their environment is becoming more and more dirty

B．the traditional ways of treating wastes are not efficient

C．they are short of useful materials

D．they need new materials made from garbage

A lot of cities are trying new ways to treat garbage mainly because ______.

A．their environment is becoming more and more dirty

B．the traditional ways of treating wastes are not efficient

C．they are short of useful materials

D．they need new materials made from garbage

A.support

B.carry

C.design

D.raise