______ a certain doubt among the people as to the practical value of the project.
A. It has B. They have C. It remains D. There remains
Remember that you won't be able to cancel the contract ____you've signed.
A. before B. until C. once D. though
Leonardo da Vinci (1452-1519) ____ birds kept in cages in order to have the pleasure of setting them free.
A. is said to be buying B. is said to have bought
C. had said to buy D. has sad to have bought
They paid fifty percent of _____ they were able to earn to the state．
A．that B．which C．what D．whom
My sister is _______ about what she eats, otherwise she would not be so thin.
A. special B. curious C. particular D. specific
I know a little bit about the city as I __________ there for one year in my youth.
A. am studying B. had studied C. studied D. have studied
