Answering questions with countable vs. uncountable nouns

A very common mistake among English learners is the wrong use of countable and uncountable nouns. While the best way to avoid the wrong usage is to memorise which nouns are countable and which ones are not, there are a few tricks to determine whether a noun is countable or not. The difference between countable and uncountable nouns is that countable nouns can be in either singular or plural forms, but uncountable nouns can be only singular.
In addition to that, countable nouns can come after “a” and “an”, but uncountable nouns cannot.
Therefore, you should know whether the word given is countable or uncountable as it affects the determiner and the –s/-es suffix (a suffix is the ending of a word).
Let’s look at the following example:

1. We still need _______ to support this theory.
          a) more evidence
          b) more evidences
          c) many evidences
          d) an evidence
The missing word is definitely “evidence”, which is given with different determiners and some end with “-s”.
Since “evidence” is an uncountable noun, “evidences” is incorrect as well as “an evidence”. Remember, only countable nouns can have an article before the noun. Uncountable nouns never have the determiner “many” in front of them (that only works with countable ones). Therefore, the correct answer is a) more evidence.
Look at the next example:

2. All online __________ should be made through a secure server.
          a) purchase
          b) purchases
          c) purchasing
          d) that purchase
The word “purchase” in this context is a countable noun which means something that you have bought. Preceded by “all”, it should be in plural form. Therefore, the correct answer is b) purchases.