She loves music and is now learning to playan ____________.

It was difficult to tell whether he could __________　our team and work for us for that situation?

―There is too much salt in the Chinese diet.―Right. The WHO says only 1.5 grams of salt ______ for each man every day.

__, no one is sure whodiscovered America

_____ maths is concerned, Tom is the best student in our class.[ ]