SDH相对于PDH的特点是()
A开销低
BSTM-4以上国际标准统一
CSDH比PDH频带利用率高
D可以进行最佳路由选择
What made it possible for the American women to have the custom of wearing lace veils at weddings？
A. The increased appreciation of lace.
B. The importation of lace.
C. The invention of the lace making machine.
D. The importation of lace making machines.
Whats the main task for "Deep Impact" this time？
A. To visit other planets.
B. To destroy the comet.
C. To collect scientific data.
D. To test the possibility of unmanned spaceship.
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