SAT语法中also和and可连用吗?Some plants use chemical signals that repel insects,and ((also,these)) signals help to put neighboring plants on alert so they can mount their own defenses答案是打括号的地方错了,The error in this sentence

SAT语法中also和and可连用吗?Some plants use chemical signals that repel insects,and ((also,these)) signals help to put neighboring plants on alert so they can mount their own defenses答案是打括号的地方错了,The error in this sentence
SAT语法中also和and可连用吗?
Some plants use chemical signals that repel insects,and ((also,these)) signals help to put neighboring plants on alert so they can mount their own defenses
答案是打括号的地方错了,
The error in this sentence occurs at (B),where the adverb "also," in addition to the conjunction "and," results in wordiness
可是and与also连用不是很多的吗,如：She sings beautifully and also plays the flute and piano.（from朗文字典）
引自SAT语法中另一道题
34.The Bactrian camel is well adapted to the extreme climate of its native Mongolia,having thick fur and underwool that keep it warm in winter and also insulate against summer heat.（正确答案）
这里不是也连用and also了吗?
是不是仅仅因为那个逗号多余?还有,also放在be动词的前后有讲究吗?
如果以上一句话改为
Some plants use chemical signals that repel insects,and these signals also help to put neighboring plants on alert so they can mount their own defenses.
另外，He is also a doctor.He also is a doctor 我好像都看到过

SAT语法中also和and可连用吗?Some plants use chemical signals that repel insects,and ((also,these)) signals help to put neighboring plants on alert so they can mount their own defenses答案是打括号的地方错了,The error in this sentence
一、also既可以用作副词（或者叫做修饰性副词）又可以用作连词（或者叫做连接性副词）.
 
　　1、作为副词（修饰性副词）,also表示“也/同样”,和 too 意思相近,只是在语气上比too更正式.also 原则上要出现在be后,实意动词前和第一个助动词（或情态动词）后,但不用于句尾,而 too 则通常用于句尾.如：
 
He is also a doctor. (或者He is a doctor, too.)  【不能说He also is a doctor】
He's a singer and an actor, too. (或者He's also a singer and an actor.) 他是个歌手,同时也是演员.
 
　　同时also作为副词也可以出现在带有连词的句子中.（例句见下）
 
　　2、作为连词（连接性副词）,also表示“而且/此外”,与and的意思相近,二者不能重复使用,否则就是赘词.
 
二、问题中的also 和and的用法分析
 
Some plants use chemical signals that repel insects, and (also, these) signals help to put neighboring plants on alert so they can mount their own defenses.   ——句中的and和also（即使后面没有逗号）都是连词,重复出现就是wordiness
 
　　但是可以把also放在动词help前：
 
Some plants use chemical signals that repel insects (and) these signals (also) help to put neighboring plants on alert so they can mount their own defenses. ——本句中的and是连词,而also变成了副词,不过在意思上有了改变.前者意思是“同时（而且）这些信号有助于…”,后者意思是“同时（而且）这些信号也（还）有助于…”
 
The Bactrian camel is well adapted to the extreme climate of its native Mongolia, having thick fur and underwool that keep it warm in winter and also insulate against summer heat. ——定语从句中的also出现在实意动词insulate前,因此是副词,与它前面的连词and在意思上并没有重复,连词and 表示“并且/此外/另外”,副词also表示“还/也”,即“厚厚的皮毛可以使双峰骆驼在冬季保温,而且（这样的皮毛）还能阻隔夏日的炎热”.
 
另如：
She has a reputation for brilliance. Also, she is gorgeous. 【also 是连词】
She has a reputation for brilliance, and, she is also gorgeous. 【also 是副词】

语义问题
都可以

also作为副词，有动词前面、Be动词后面的说法，你可以照此验证。