Step 1: Understanding the Task
The task is to find any grammatical error in the given sentence. The sentence is structured as a definition.
Step 2: Analyzing the Sentence Structure
The main subject of the sentence is "The substances". The phrase "which are added to the soil in the form of nutrients" is a relative clause modifying "substances". The phrase "for the healthy growth of plants" is a prepositional phrase of purpose. The main verb of the sentence is "are called", which corresponds to the plural subject "substances".
Part (a): "The substances which are added to the soil in the form of nutrients" - The subject "substances" is plural, and the verb in the relative clause "are added" is also plural. This is correct.
Part (b): "for the healthy growth of plants" - This prepositional phrase is grammatically correct.
Part (c): "are called manure and fertilizers" - The main verb "are called" is plural, correctly agreeing with the subject "substances". This part is correct.
Step 3: Identifying the Error
There are no subject-verb agreement errors, incorrect pronouns, or other grammatical mistakes. The entire sentence is constructed correctly.
Step 4: Final Answer
The sentence is grammatically correct. Therefore, option (D) is the correct answer.