题目

根据短文内容选择正确答案。If you plan to take your pet on a trip, prepare ahead of time(提前). At least two weeks before you leave, take your pet to a vet. See if he or she is fit for travel and ask if he or she should have any medicine before leaving. The vet may suggest(建议) certain pills for sickness or for calming the pet.Some states or foreign countries have health laws that say animals must have certain injections(注射)before they can be allowed(允许) to enter. Your vet may have this information. You can also get help on the United States and Canadian laws from a bo下列计算正确的是（　　）A．3a+2b=5abB．-2a2b+3ab2=a2b2C．2a2b-3a2b=-a2bD．3x2-4x5=-x3