这块面包放太久，已经硬得像石头了。

The bread was left out too long and now it's ___rock-hard.

经过多年的训练，他的腹肌变得像石头一样坚硬。

After years of training, his abs have become ___rock-hard.

尽管遭遇失败，他依然坚定如岩石般毫不动摇。

Despite the failures, he stayed ___rock-solid in his beliefs.