关于not only but also 连接谓语时的问题

关于not only but also 连接谓语时的问题
其中一个谓语是be动词,另一个是其他动词时该怎么用.比如
a、Mary not only is very kind but also can do housework.
b、Mary is not only very kind but also can do housework.
哪个对呢.或者不能这么用.
能不能加一个频率副词呢.比如：
I not only listen to the music bot also watch TV after school.
English was not only used in science but also can help us watch English movies.
能不能在上两句加一个频率副词often.如果能.在哪加.