If people eat natural poisons by mistake, they ________ go to hospital without delay.

E-mail, as well as telephones, ________ an important part in daily communication

You don’t need to describe her. I ­­­­______ her several times.

We did everything we could________ him to stay，but he insisted on leaving.[ ]

．—What’s the matter with the man hanging his head there? —Well, if you _______ know, he was caught stealing my bike.