_________ useful dictionary it is!It's very helpful for English study.( )
What a
What an
How a
How
Those young firemen were brave enough to __________ the fire in the forest.( )
A.work outB.put outC.hand outD.look out
What is your mother doing, Linda?
She ___________dinner in the kitchen now.( )
A.is cookingB.was cooking
C.cookD.cooking
__________ the help of modern technology, scientists got a photo of a black hole.( )
A.AtB.InC.OnD.With
Will you stay here for dinner with us?
Sorry, I ____________. My mother is waiting for me at home.( )
A.mustn'tB.can'tC.needn'tD.couldn't
What do you think of working as a doctor?
It 's a good job to help people keep___________.( )
A.busyB.strictC.healthyD.generous