用滴管从瓶中吸取酒精，滴在手上，感觉凉凉的，小明就这一现象产生的原因，提出了两种猜想，猜想1 ：酒精的温度低于手的温度；猜想2 ：酒精蒸发时吸热，有致冷作用，随后，他在烧杯中倒入适量酒精，用相同的温度计分别测量手的温度t1和烧杯中酒精的温度t2，并重复多次，均发现t1>t2，由此，他[ ]

A. 只能验证猜想1

B. 只能验证猜想2

C. 既能验证猜想1 ，也能验证猜想2

D.  既不能验证猜想1 ，也不能验证猜想2

Why is (21) fun What delights may its practitioner expect as his reward First is the sheer joy of making things. As the child delights in his mud pie, so the adult enjoys building things, especially things of his own design. Second is the pleasure of making things that are useful to other people. Third is the fascination of fashioning complex puzzle-like objects of interlocking moving parts and watching them work in subtle cycles, playing out the consequences of principles built in from the beginning. Fourth is the joy of always learning, which springs from the
(22) nature of the task. In one way or another the problem is ever new, and its solver learns something:sometimes (23) , sometimes theoretical, and sometimes both. Finally, there is the delight of working in such a tractable medium. The (24) , like the poet, works only slightly removed from pure thought-stuff. Few media of creation are so flexible, so easy to polish and rework, so readily capable of realizing grand conceptual structures.
Yet the program (25) , unlike the poet’s words, is real in the sense that it moves and works, producing visible outputs separate from the construct itself. It prints results, draws pictures, produces sounds, moves arms. Programming then is fun because it gratifies creative longings built deep within us and delights sensibilities we have in common with all men.

A．semantic

B．practical

C．lexical

D．syntactical