The engineer ______ my father works is about 50 years old.
D
withwhom引导定语从句.withwhom放在从句中即为:myfatherworkswiththeengineer
Iaskedhimto________meafewminutessothatwecouldgooveralltheproblems.
Thereisadeadlock(僵局)inthediscussionwhenneithersidegives________totheother.
Thisisanimportantproblem_______toofewsocialscientistshaveresearched.