被科学家选为植物的模式生物的是()。
A.水稻
B.芦苇
C.胡萝卜
D.拟南芥
参考答案:D
因式分
(1)-3x3+6x2y-3xy2
(2)x4-9x2
(3)(a-2b)2-25b2
(4)(m2-1)2+6(1-m2)+9.
They no longer have to ______ large numbers of temporary workers to do the harvesting.[ ]
A. take on
B. hire on
C. work on
D. carry on