龙蒿是一种多年生的草本菊科植物，含挥发油，主要成分为醛类物质，还含少量生物碱。青海民间入药，治暑湿发热、虚劳等。龙蒿的根有辣味，新疆民间取根研末，代替辣椒作调味品。俄罗斯龙蒿和法国龙蒿，它们看起来非常相似，但是俄罗斯龙蒿开花而法国龙蒿不开花，而且俄罗斯龙蒿的叶子却没有那种使法国龙蒿成为理想的调味品的独特香味。
若植物必须先开花，才能产生种子，则从以上论述中一定推出以下哪项结论?

A -2x²cosx⁴． B <img width="187" height="43" src="https://www.beizhujiaoyu.com/uploads/202208/20211222222846_2105.jpg" /> C <img width="190" height="44" src="https://www.beizhujiaoyu.com/uploads/202208/20211222222847_2886.jpg" /> D <img width="86" height="43" src="https://www.beizhujiaoyu.com/uploads/202208/20211222222848_3199.jpg" />

A 0． B 1． C 2． D <img width="24" height="36" src="https://www.beizhujiaoyu.com/uploads/202208/20211222222850_4292.jpg" />

A 充分必要条件． B 充分条件但非必要条件． C 必要条件但非充分条件． D 既非充分又非必要条件．

A 2x-2． B 2x+2． C x-1． D x+1．

A 1． B x²． C e^x． D 2x．

A 0． B <img width="23" height="41" src="https://www.beizhujiaoyu.com/uploads/202208/20211222222854_6636.jpg" /> C 1． D <img width="24" height="41" src="https://www.beizhujiaoyu.com/uploads/202208/20211222222855_7818.jpg" />

A <img width="24" height="41" src="https://www.beizhujiaoyu.com/uploads/202208/20211222222857_8980.jpg" /> B <img width="24" height="41" src="https://www.beizhujiaoyu.com/uploads/202208/20211222222858_8845.jpg" /> C <img width="23" height="41" src="https://www.beizhujiaoyu.com/uploads/202208/20211222222900_0084.jpg" /> D <img width="23" height="41" src="https://www.beizhujiaoyu.com/uploads/202208/20211222222900_9917.jpg" />

A 1． B 2． C 3． D 4．

A 5． B 10． C 20． D 40．

A α₁必可由α₂，α₃，α₄线性表示． B α₂必可由α₁，α₃，α₄线性表示． C α₃必可由α₁，α₂，α₄线性表示． D α₄必可由α₁，α₂，α₃线性表示．