几个关于情态动词选择的问题
1.I ____ walk properly since i had that skiing accident.
答案是haven't been able to为何couldn't不可以？
2.Students ____ wear school uniforms when they have an important meeting.
答案是have to为何must不可以？
3."Why are you and Jack arguing so much these days?"
"He takes me for granted.He ____watch TV every evening and ignore me completed."
答案是wil表示“通常”，但为何should表示“竟然”不可以？
4.I ___ pay Tracy a visit,but i'm not sure whether i will have time this Sunday.
答案是should为何must不可以？
以上，谢谢了！！