正确语序：A Did your mother stay at home last night?
B:Were you in last night?
C.对的
D：Did your mother stay at home last night?
首先 stay at home = be in
但是正确表达第三人称your monther 是单数,又是过去时last night,所以用was 或者 stayed
You是第二人称,一般现在使用are,一般过去式用were.
一般疑问句,be动词提前或者 助动词Did提前动词过去式变原型.
以此类推