Answer:
The answer is indeed the noun "rain".
Explanation:
Noncount or uncountable nouns are those that represent something that cannot be divided into individual units and counted. They may refer to a mass, a natural substance, a food, a language, a feeling or any other abstract concept etc. - but there are exceptions. Examples of noncount nouns are: water, air, hair, money, homework, coffee, bread, Chinese, swimming etc.
We must keep in mind that a noun that is uncountable in English can be countable in another language. Also, most uncountable nouns do not have a plural form (information), while others occur only as a plural noun (pants).
In the sentence "The rain started to fall in the early hours, and soon, the backyard was flooded", we are provided with three nouns: rain, hours, and backyard. It is possible to count hours - we actually do it all the time. It is also possible to count backyards. Both words present a plural form as well as a singular one. However, it is not possible to count rain. We do not look up at the sky and say, "Look! So many rains! One rain, two rains..." Rain is noun that refers to an unspecified number of water drops. It is impossible to count.
