单项选择题 If you can't dig into the field you have chosen for your pursuit, it is hardly possible for you to achieve anything significant in the field（）.

单项选择题 The old man sat before the fire in a trance, thinking of his past fife（）.

单项选择题 The sense of mistrust is compounded by smaller annoyances that leave the families feeling as though no one in authority cares about them（）.