help grammar please

<p>hey :) i have two questions for u :p
1 .
can we say " and whereby " or it must be " whereby +ing "
2.
"some" is singular or plural right ? we have to look at object of prep
but look here
some types of algae HAVE so high...bla blaa
how come here have ? !! shouldn't it be has bcz of algae
thank soooo much :)</p>

<ol>
<li><p>It isn’t illegal to use “whereby.” To what context do you refer? Use it in a sentence and we’ll tell you whether it works.</p></li>
<li><p>Not sure what you’re asking. Again, if you could post a specific sentence then you’d probably get more helpful responses.</p></li>
</ol>

<p>some types of algae HAVE so high content that scientists are seeking cost-effective ways.
this sentence has no error
but iam confused shouldn’t it be HAS as some is an indefinte prooun and we should look at object of pp</p>

<p>Some can be an indefinite pronoun, but it isn’t one in this sentence. It’s an adjective modifying types. The noun types, which is plural, is the subject of the sentence; that’s why have is the correct form of the verb.</p>