The period ________ dance classes increases gradually from two or three hours a day to five or six.
A．referred to B．kept to
C．got to D．given to
The period ________ dance classes increases gradually from two or three hours a day to five or six.
A．referred to B．kept to
C．got to D．given to
D given to dance classes为过去分词短语作后置定语，相当于that was given to dance classes, 意思是“分给舞蹈课的时间”。