summit

The road to social mobility … it is an agonisingly steep path up a

mountain whose summit is never quite in view。

peak

If a person finds getting up early a problem, most probably he is

at his peak in the afternoon or evening.

vague

Researchers … found many too vague or too misleading to meet

ISO standards.

doubtful

The author is doubtful about the necessity of keeping H-bombs

at home for safety.

dim

The elderly man suggests having a brighter bulb some where

because this light is too dim for us to read by.

sour

A: Geez! The milk gets sour. It makes refrigerator smelly.

B: Throw it away.