It was not until she had arrived home ( ) remembered her app

这句是强调句,强调时间,补充完整应该是：
It was not until she had arrived home (that she) remembered her appointment with the doctor.
她到了家才想起她和医生的预约.
你这里的选项没有正确答案.
ps.强调句的句型it is(was)...that/who(whom)...
强调人时,用who或whom
强调其他时,一律用that