________there are a large number of chemical factories, the air is likely to be polluted.

________there are a large number of chemical factories, the air is likely to be polluted.

A．Where           B．That　　　　      C．Though           D．As

 ________ there are a large number of chemical factories, the air is likely to be polluted.

A. Where         B. That           C. Though        D. As

________ there are a large number of chemical factories, the air is likely to be polluted.

[　　]

________ there are a large number of chemical factories, the air is likely to be polluted.

[　　]

A．That　　　　　B．Once

C．Where　　　　D．Which