At a college football game,

of the seats in the lower deck of the stadium were sold. If

of all the seating in the stadium is located in the lower deck, and if

of all the seats in the stadium were sold, what fraction of the unsold seats in the stadium were in the lower deck

边坡最易发生顺层滑动的岩体是()。

A．原生柱状节理发育的安山岩

B．含黏土质页岩夹层的沉积岩

C．垂直节理且疏松透水性强的黄土

D．原生柱状节理发育的玄武岩