The dentist () his decayed tooth again.

单项选择题Because the region was served by a railroad line, with station stops from three to five mites (), there was a natural limit to the spread of any particular community.

A. distance
B. away
C. after
D. apart

单项选择题My supervisor advised me to () the problem.

A. look ahead
B. look down on
C. look out of
D. look into