cognate languages are those languages which:

Question

A}Derive from a single parent language.
B}Borrow words from each other
C}Use the same alphabet
D}Are spoken in the same country
.The answer i choose is B.

Answer 1

There is a difference between cognate languages and cognate words. When cognate words (that are spelled the same or similarly) mean the same thing in different languages, it can be because they derive from a common parent language (e.g. Latin or old German) OR because one language adopts or "borrows" the word from another (e.g "pajamas" Persian and Hindstani, or "vodka" from Russian). Many words are now borrowed from English into other languages

When one speaks of languages as being cognate or "sister" languages, it is because they derive from a single parent language. Answer A is the correct one in this case.