______ students should be given more freetime is suggested by many experts and welcomed by kids in school

32．She shouldn’t be working so hard —She is 70, ___

May I borrow your pencil, please -of course, here are two and you can use __of them.

My parents _______ have arrived at suppertime but their flight was held up due to the heavy fog.

Achieving a high degree of proficiency(精通）in English as a foreign language is not a mysterious _______ without scientific basis.