正三棱锥A—BCD的体积为（ ）．

单项选择题A．<br ><img src= {$uploaddir} ea1b4302-f3df-4a9c-8d3b-6cf2ac87f52e.jpg >B．<br ><img src= {$uploaddir} 601c8ddf-c709-438a-b1ed-de2421d118c7.jpg >C．8D．12

单项选择题已知集合A={x|5x-a≤0}，B={x|6x-b＞0}，a∈N，b∈N(其中N为自然数集)，且满足(A∩B.∩N={2，3，4}，则整数对(a，b)的个数为（ ）．

单项选择题该处选项为（）。

A．This tour is the chance of lifetime．
B．It goes all over North America and South America．
C．It looks like you’re dreaming about something．
D．You’ll have to quit school and your job at the store．
E．My agent wants me to go on a tour with Art’s Jazz Band．
F．Have you told anyone about this yet
G．It would be a great opportunity!

单项选择题A．<br ><img src= {$uploaddir} 07679be7-0491-4a9d-a0ae-0bad3a665d87.jpg >B．<br ><img src= {$uploaddir} a04ee98d-9e30-4f85-853d-83500c918f51.jpg >C．<br ><img src= {$uploaddir} 375d828d-6f3d-4261-a47b-c6c079197ab1.jpg >D．<br ><img src= {$uploaddir} dfbe9607-8be0-4618-aaba-baa0e9baee80.jpg >

单项选择题A．m≤-1B．m＞1C．0＜m≤1D．-1≤m＜0