Question

He is the only one of the students ___late this morning. A.who was B.who were C.that were D.whom wa

为什么不选that？ 如果只是单复数的原因，那如果有 that was 这个选项，应该选哪个？
D选项是 whom was

Answer 1

这迟汪蔽道题应该选A，从单复数的码州原因上排除陵唤B.C，主语HE在定于从句中作主语，因此只能用who，不能用whom，whom只有主语在从句中作宾语时可用。
如果有that was就也可以选，因为定语从句中that可以指代人或物。

Answer 2

选A