Bigtable表中的数据是通过（）来进行索引的

A、行关键字

B、列关键字

C、子表地址

D、时间戳

What does the passage mainly discuss

A．The endangered species in Glacier National Park.

B．The protection of lands surrounding Glacier National Park.

C．Conservation laws imposed by the state of Montana.

D．Conservation laws imposed by Congress.