控制人类肤色的基因为两对基因（A-a，B-b），它们以累加效应决定人的肤色，黑种人基

San Francisco has many museums. You can visit one and learn something new, We have art, science, history and other special museums. Some museums are open every day. Some are only open on certain days. Many museums are expensive, and others are free. But some of the expensive ones have free days. May museums have websites. The websites usually have information about the things you can see in the museums.

On a museum's website you can get information about .ticket prices and free days. You can also know where the museum is and when it is open. Sometimes the information is on the first page, and it's very easy for you to find. But sometimes you have to click (点击)  on the words like Visit Information, or About to find the information. That will be hard work for you.

小题1:San Francisco has many museums for you visit and                .

A．learn something new

B．play computer games

C．watch the movies

D．click on Information小题2:Some museums in San Francisco are open every day, but some are only open           .

A．on weekdays

B．on weekends

C．on certain days

D．on holidays小题3:Many museums have             with information about the things you can see in them.

A．ticket prices

B．their websites

C．open hours

D．free days

在建设项目组织管理中应用互联网的项目信息门户有着重要的意义，下列说法错误的是( )。

A．降低了工程项目实施的成本
B．缩短了项目建设时间
C．降低了项目实施的风险
D．降低了业主的满意度

债权人决定将其债权债务一并转让给第三人时，( )。

A．须经对方同意

B．无须经对方同意，但应通知对方

C．无须经对方同意，也不必通知对方

D．须经对方同意，但要办理公证

带电作业时人体表面裸露部位的电场强度不应超过人体的感知水平24kV/m。

节理的力学成因类型有（）和（）。