Tính bằng cách hợp lí nhất: 1 4 + − 5 13 + 2 11 + − 8 13 + 3 4  

Cho tam giác ABC cân tại B. Gọi Bx là tia phân giác của góc ngoài tại đỉnh B. Chứng minh Bx //AC.

Read the following passage and mark the letter A, B,C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

Working mothers

  Because an increasing number of people are opting to work outside the traditional office, notebook PCs are becoming more and more popular. However, you should know that notebook PCs aren't for everyone. As you (27) ___________ up the pros and cons of your desktop PC with a new system, you should bear (28) ____________ mind that you may get better profit for your money by investing in a faster, more powerful desktop PC.

          Portability comes at a price. Leave your laptop unattended for any length of time in any sort of public place and you will quickly discover that it has been stolen. You could even lose it without any intentional neglect on your area; laptops (and all the business and personal information they contain) are easy (29) _____________ for skilled thieves. So, yes, there are definitely serious security issues. Also, if you are prone to tossing your laptop around as you do your purse, workout bag or umbrella, you’ll probably break it before you get your money's worth. Guarantees are getting better and longer, but they still won’t cover a simple slip, let alone (30) _____________ carelessness. So, before you (31) _________        out to get yourself the latest technological appliance, think long and hard as to whether a notebook PC is really suitable for you.

Điền vào ô 30.

A. usual

B. normal

C. regular

D. habitual