下列与生物遗传有关的叙述，正确的是（ ）
| A．基因型为Aa的个体连续自交3代后，子代中隐性性状个体所占的比例为3/8 |
| B．已知黑斑蛇与黄斑蛇杂交，子一代既有黑斑蛇又有黄斑蛇，若再让F1黑斑蛇自由交配，F2中有黑斑蛇和黄斑蛇，可据此判断蛇斑的显隐性 |
| C．基因分离定律的实质表明，基因型为Bb的动物，在其精子形成过程中，基因B与B分开发生在初级精母细胞形成次级精母细胞时，B与b的分开发生在次级精母细胞形成精细胞时 |
| D．用豌豆进行遗传试验，杂交时须在开花前除去母本的雌蕊，人工授粉后应套袋 |
Mandeep can go to school now. UNICEF has paid for her ______.
| A．education | B．vacation | C．competition | D．invention |
Lucy liked all the dresses there，but she took the ______one to save as much money as possible for Project Hope.
| A．cheaper | B．more expensive | C．cheapest | D．most expensive |
一Look! That teacher is explaining something to her students again and again!
一_______teacher she is!
一_______teacher she is!
| A．How patient | B．What patient | C．How a patient | D．What a patient |
David didn’t give up ______ he had failed in the experiment four times.
| A．if | B．while | C．though | D．since |
Wearing white can help people _______when they feel stressed.
| A．fall down | B．calm down | C．look down | D．come down |
Linda, with her parents，_______ the Wolf Hill, and they will be back this afternoon.
| A．has gone to | B．have gone to | C．has been to | D．have been to |
For everyone’s safety，we _______ a1ways remember the law against driving after drinking.
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| A．could | B．should | C．might | D．would |