When ______ comes to research into heart disease and its effects on the body, we do not have adequate substitutes for the use of animals.

— I wonder ________ you’ll water this kind of flower. 
—Once a week.

— Do you know Jim quarreled with his mother?
— I don’t know. _____.

I really don’t know _____ I put my wallet after I paid the bill.

---Did Mark win the 100-meter race?
---     . He did _____ I.

That is secret．        ．
? 

Only when you told me about it ________ what a silly thing I had done.

Under no circumstances, he was warned, _____ to give the password to someone else.

Not until the car looked almost new____ cleaning it.1网

Looking out of the window of my room, ___ a tall tree in the yard.