plural /singular

Sentence 1 : In one of the researches conducted by the scientists , they found trybutyltin contamination on the rock shell, which existed in the sea especially at busy ports.

My question is : is it correct to pluralise " researches" ?

Sentence 2: According to the text , City Hall and Department of Irrigation have different jurisdictions to prevent flood from happening .
What are they ?

My question :Is the sentence " What are they " correct ?

Sentence 3 : This is because the foulant tend to slow down the ship thus increasing fuel consumption .

My question : The word " tend ", shouldn't it be "tends" because the noun is singular ?

[RonBee]

1. Yes, you can pluralize research. If you use researches that denotes more than one investigation.

2. The question "What are they?" asks "What are those different jurisdictions?" It ("What are they?") is correct, but it can be confusing.

3. Yes, I think so. It should be tends.

[Edited to spruce up the posting.]

1. Research is an uncountable noun and, therefore, can never be in the plural. However, there is a way of making an uncountable noun plural, and that is by adding another noun to make a compound noun:

In one of the RESEARCH STUDIES/ PROJECTS conducted by the scientists...

2. For a start it should be THE Deprtment of Irrigation. Secondly I don't think the word JURISDICTION is what you want here. A jurisdiction is an area that is governed. A jurisdiction cannot prevent flooding! Maybe:

...have different PROCEDURES to prevent FLOODING....

Consequently, the question "What are they?" is correct.

3. Yes, it should be TENDS.

[RonBee]

Normally, research is not pluralized, but it can be and is.

research
noun (plural re·search·es)
http://encarta.msn.com/encnet/featur...fid=1861700688

researches
plural noun
His researches (= research) in the field of disease prevention produced unexpected results.

(from Cambridge Advanced Learner's Dictionary)
http://dictionary.cambridge.org/defi...&desc=research

:)