English grammar error-spotting (subject–verb agreement with ‘‘the number of …’’): Read the sentence in four parts (A–D) and select the erroneous segment; choose ‘‘No error’’ if none: ‘‘When we consider all the factors, which are many, / the number of school dropouts / are quite disturbing. / No error.’’

Given data

• A: Context clause
• B: Subject = ‘‘the number of school dropouts’’ (singular head ‘‘number’’)
• C: Predicate verb = ‘‘are quite disturbing.’’

Concept / Approach
With ‘‘the number of + plural noun’’, the grammatical subject is singular (‘‘number’’), so the verb must also be singular: ‘‘is’’ not ‘‘are’’.

Step-by-step check
Change Part C to ‘‘is quite disturbing.’’

Common pitfalls

• Confusing ‘‘the number of’’ (singular) with ‘‘a number of’’ (plural meaning ‘‘several’’).

Final Answer
are quite disturbing.