受精作用最重要的意义是[ ] A．增加了生物的变异性 B．保持了前后代体细胞质的

物质的量浓度相等的下列溶液pH值由大到小的顺序是

A．Na₂CO₃、NaHCO₃、NaCl、NH₄Cl

B．Na₂CO₃、NaHCO₃、NH₄Cl、NaCl、

C．Na₂CO₃、NaCl、NH₄Cl、NaHCO₃

D．Na₂CO₃、NH₄Cl、NaHCO₃、NaCl、

如图所示，被固定好的激光源L发射的一束激光照射到容器中的水平液面上，入射角为α?。这束激光经液面反射后，照射到光电转换器M的D1点上，光电转换器M能够将接收到的光信号转换成电信号，从而指示出容器中液面的高度。经过一段时间后，如果光信号由D1点移至D2点，说明容器中的液面________了（填“升高”或“降低”）。此时的入射角_______?α（填“大于”、“小于”或“等于”）。

If you find you spend more than you make, there are only two things to do: decrease your spending or (1) . It’s often easiest to decrease expenditures, because your expenses tend to be more (2) . There are as many ways to (3) as there are people looking to save it. For example, you may pool your resources with friends, or (4) only during sales, or even live more simply. But (5) that saving money should not necessarily be an end in itself. Don’t (6) of ways to save a dime, and don’t get upset about situations where (7) to spend money. The goal is to bring your budget into balance, not to become a tightwad who keeps (8) of every penny and feels that spending money is a (9) . It is important to remember that budgets may be (10) not only by decreasing expenditures, but also by increasing income. (11) to increase income is to get a (12) if you don’t already have one.
Many students work during college. Although working adds to the (13) you will face, it does not mean that your grades will necessarily suffer. In fact, many students who work (14) than those who don’t work, because those with jobs need to be (15) . Considering part-time work is often a better (16) for dealing with budget shortfalls, than taking out a loan. Because student loans are (17) , it’s easy to use them as a crutch. Loans can be of help (18) or if you couldn’t afford to attend a college without them. If you do (19) , remind yourself: one day soon you’ll have to (20) with interest.

双重代理可以同时向买卖双方收取佣金，佣金总额一般高于前两种代理形式()

日常管道施工中，常用的割管器有（）种型号。

A.2

B.3

C.4

D.5