4．下表为光照和含生长素的琼脂块对水稻种子根尖弯曲生长的影响，相关说法正确的是 A．表格中a表示“向贴有琼脂块一侧生长” B．①组与③组说明
有关声现象的下列说法中不正确的是（ ）A．男低音独唱时由女高音轻声伴唱，则男低音比女高音音调高，响度大B．男低音独唱时由女高音轻声伴唱
下列有关基因重组的叙述,正确的有( ) ①姐妹染色单体间相同片段的交换导致基因重组 ②基因型为Aa的个体自交,因基因重组而导致子代发生性状分离 ③
二次函数f(x)的图象如下图所示，则f(x-1)＞0的解集为( )A.(-2,1) B.(0,3) C.(-1,2) D.(-∞,0)∪(3,+∞)
当化学反应的△H＜0,△S＞0时，反应一定能自发进行。下列反应属于该情况的是（ ） A． Zn(s)+2HCl(aq) = ZnCl2(aq)+H2(g) B．2H2(g)+O2(g) = 2H
Although there were so many people in the square, I could ______ my friend. A. pick up B. pick out C.
[1]Surveys find that half of American teenagers are missing an average of up to 1.5 hours of sleep every school night. [2]Surveys of American teenagers find that about half of them do not get eno
下列可用于脂肪鉴定的实验材料是( ) A. 苹果 B. 梨 C. 鸡蛋清 D. 花生种子
