题干
These days he has made _____ in his studies by working hard.
A：many progre
B：a lot of progresse
C：much progre
D：many a progre
答案(点此获取答案解析）
C
A：many progre
B：a lot of progresse
C：much progre
D：many a progre
，河水流速为
，划船速度均为
，出发时两船相距
，甲、乙船头均与岸边成60°角，且乙船恰好能直达正对岸的
点，则下列判断正确的是 
