I tried ________ it out in this way, but I failed (失败)．—Why not ______ it in some other ways

nk coulduswith $100,000 for the house．Why don’t we buy it

They will start their project，________at helping the poor children to be educated inthe west of China.

Scientists are convinced ______ the positive effect of laughter ______ physical and mental health.

Look! The young girl is dressing up _____ an old woman ______ a black coat.