根据短文内容，从短文后的选项中选出能填入空白处的最佳选项，选项中有两项为多余选项。
Taking a math test can be pretty stressful. Even if you know the material, you can still get the problem wrong. Knowing how to go through your math test and check your work can save you from handing in a test full of mistakes that can be avoided.    
Write it out
You can also check a math problem by writing everything out on paper.     Writing out math problems reduces your chances of missing anything to the lowest possible level, which is a common cause of incorrect answers.
  
Make sure your answers work by doing the opposite procedure of what your problem calls for, including the answer you got the first time around. In other words, you would use the opposite of this addition problem—subtraction (减法)—to determine whether or not your answer is the correct one.
Plugging in
You may find that a variable(变量) isn’t good enough or have a problem where you have to solve for a variable.     This is the only real way to assure yourself that the answer you’ve found is correct.
Check for a reasonable answer
    For example, if you get an answer in the millions and you know it should be in the thousands, you’ve likely misplaced a point. Go back through the work on your paper to make sure all of your formulas and calculations are correct. If everything looks okay, do the problem again and compare the result of the second try to what you’ve got on the first try.

A．Do the opposite

B．Correct the answers

C．Plug the variable in the equation (方程) to check it out.

D．Therefore you’ll improve your grades, as well as your math skills.

E. It also helps you to figure out everything after you have already finished the test.
F. If the result of a problem seems to make no sense, it indicates that the answer is incorrect.
G. This helps you to know what information you have and what information you need to solve.