Chinese structure is based on the principle of balance and symmetry.

A、Why do prices in general rise by more in some countries than in others?

B、How rapidly is GDP currently increasing?

C、Why do production and income increase in some periods and not in others?

D、Why do wages differ across industries?

For the long run variance-covariance estimator=()(j)， when n is large enough, we can let= [], where [x] is the largest integer that is not greater than X.

A、极位夹角θ=0°

B、压力角α=90°

C、传动角γ=90 °

D、压力角α=45°

Summary of the Text To my son, I am a (1)_____________: a father he is (2)__________ listen to and a man (3)____________ the rules of grammar. And I got (4)______________ this because my student was unable to describe properly her feeling on her (5)__________ to Europe. However, it doesn't (6)________________ to criticize our students. They unfairly bear the bulk of the criticism for these (7)__________________ because there is a sense that they (8)_________________. On one hand, they are misled by the (9)____________. On the other hand, school fails to (10)_________________ the essential framework of language, (11)_____________grammar and proper vocabulary. Perhaps, language should be looked upon as a (12)_________ and a (13)___________________: often study the road map (check grammar) and (14)________ the car engine (adjust vocabulary). Learning grammar and a good vocabulary is just like driving with a road map in a (15)________________ car. (16)__________, (17)_________, and (18)__________ communication depends upon grammar and a good vocabulary, the two (19)__________ assets for students, but they are (20)_______________ in schools.