He tried to invite some famous pop stars to sing in the concert _____, but failed. [ ]

A. with free

B. for freely

C. with freedom

D. for free

（）位于建筑物的最下部，是建筑的重要承重构件，它承担建筑的全部荷载，并把这些荷载有效地传给地基。

A、基础

B、散水

C、地下室

D、地坪层