供应枕叶的血管为（）
A.大脑后动脉
B.颈内动脉
C.前交通动脉
D.大脑中动脉
E.大脑前动脉
参考答案：A
Which reason for purchasing U. S. Treasury securities is least valid（）
A. Coupon strips synthesize a zero-coupon bond.
B. Treasury-bonds are available in maturities of two years to nearly 30 years.
C. Treasury Inflation Protection Securities (TIPS) raise their principal value to adjust for inflation.
点P（3－a，a－1）在y轴上，则点Q（2－a，a－6）在第______象限。
