In theory... let's see -
You are tracking QDR 300º... and get that clearance, you...
(1) maintin current altitude/level
(2) turn left to track 160º, (unless given a heading) which is shortest intercept (90º) of the QDR 250º...
(3) when turning right to track the QDR 250º, you descent to 4,000 ft QNH...
xxx
As I said all this is (hmmm!) theory - in practice you would get a heading.
Some of these tests have strange questions - written by people who never fly.
Happy contrails