Scientists are convinced ________the positive effect of laughter________ physical and mental health.
| A．of; at | B．of; on | C．by; in | D．on; at |
I don’t think _______ possible to master a foreign language without much memory work.
| A．it | B．that | C．its | D．this |
Therearetworoadsandeither ________tothestation.
| A．leads | B．lead | C．areleading | D．isleading |
Whenandwherethistookplace_________stillunknown.
| A．are | B．were | C．is | D．has |
Ourfamily____ahappyone.
| A．is | B．are | C．was | D．were |
Morethanoneanswer _______tothequestion.
| A．havebeengiven | B．hasbeengiven | C．weregiven | D．hadgiven |