Spelling the "Perfect" Tenses

By next week, my class ____ ____ ______ about many different vitamins. (learn - future perfect)

Scientists ____ __________ about many different vitamins. (discover - present perfect)

I ____ _______ a report about James Lind. (start - present perfect)

I ___ never _____ of Lind before now. (hear - past perfect)

Over the centuries many sailors ____ ________ from this illness. (suffer - present perfect)

Lind ___ __________ a disease. (research - past perfect)

Lind's studies ___ _____ that lemon juice could prevent this disease. (show - past perfect)

By Monday I ____ ____ ________ an assignment on vitamin A. (finish - future perfect)

This illness ___ now ______ rare. (become - present perfect)

I ___n't ________ that carrots contain vitamin A. (realize - past perfect)