Question

Read the following sentence, spot the errors and correct them.
The telephone is an useful instrument.

Answer 1

Hint: Read the sentence, understand what it's trying to convey. Then check whether it is written well in order to convey the desired information. If yes, then go forward and look if it is grammatically sound or not.

Complete answer: In this question, it will be helpful for the student to recall the concept of a definite article and an indefinite article. A definite article is a determiner (as `the' in English) that indicates the specificity of reference. An indefinite article is a determiner (as `a' or `some' in English) that indicates nonspecific reference.
We know that an article is a determiner that may indicate the specificity of reference of a noun phrase.
In the given question, we have to find out which part/word/phrase of the sentence contains an error of any sort.
The error (s) can be either a grammatical error or a spelling error.
In the given sentence, all the words are correctly spelt, therefore, there are no spelling errors.
Now, let us look for any possible grammar-related errors –
‘The telephone’ is grammatically correct as ‘telephone’ is a noun that can be a specific reference.
‘is’ is a verb in the simple present, and here it is used to indicate a general fact. It is also grammatically correct.
‘an useful’, here the indefinite article ‘an’ has been used even though ‘useful’ starts with the consonant sound of ‘yu’.
Thus, ‘a’ should be used instead of ‘an’.
‘The telephone is a useful instrument.’

Note: Before jumping to check the grammatical correctness of the given sentence, students should always try to comprehend what the sentence wants to deliver and see whether it is written correctly to deliver the right information, with proper punctuations.