Which one of the following references is written according to American…

Concept: An APA-style reference for a book is assembled from four elements in one fixed order — author, year of publication, title of the work, and publication details — and each element is closed with a full stop before the next one begins. The author element is written as surname, comma, initial followed by a full stop; the year of publication is always enclosed in parentheses; and the publication details are given as place of publication, colon, publisher.

Application: Reading the entry "Sharma, V. (2010). Fundamentals of Computer Science. New Delhi : Tata McGraw Hill" against that pattern: the author appears as surname, comma, initial with a full stop; the year stands inside parentheses and is closed by a full stop; the title is closed by a full stop; and the publication details follow as New Delhi : Tata McGraw Hill. Every element boundary is a full stop and the year is parenthesised, so this entry is the reference written in APA format.

Cross-check: How the remaining entries depart from that pattern —

• "Sharma, V. 2010. Fundamentals of Computer Science. New Delhi : Tata McGraw Hill" keeps the APA element order and the full stops, but leaves the year unparenthesised — the plain author-date form used by Chicago and Harvard styles rather than by APA.

• "Sharma.V. 2010. Fundamentals of Computer Science, New Delhi : Tata McGraw Hill" joins the surname to the initial with a full stop instead of a comma, leaves the year unparenthesised, and closes the title with a comma instead of a full stop.

• "Sharma, V. (2010), Fundamentals of Computer Science, New Delhi : Tata McGraw Hill" does parenthesise the year, but follows it with a comma and then uses commas in place of full stops between the remaining elements.

So the deciding features are the parenthesised year and the full stops that close the author, year, title and publication elements; the reference carrying both is the APA one. (APA additionally italicises the book title, but the examination prints every entry in plain text, so punctuation is what separates the entries here.)