11+ Reading comprehension help

[SheHulk]

I am confused whether DS should answer reading comprehensions with long sentences or short ones as in:
-question: What was the name of the dog?
-long answer: The name of the dog was Snowy.
-short answer: Snowy.
Or:
-question: Why was Annie upset?
-long: She was upset because her dog had died.
-short: Because her dog had died.
His Yr. 4 teacher insisted on long answers, his Yr.5 is asking for short ones! What is the norm in the 11+ exams? We are tutoring him at home. Those of you out there with DCs who have passed them...? Should he answer long or short?

I would advise him to write a long answer. I am an English teacher and private tutor and this seems to be what is expected.

Hmm. is he managing to complete all the questions within the set time?
Longer answers showing good grammar are better, but only if he manages to answer everything. Time short, I'd go for short answers and get all the points.

Thank you both.