The question as posted may (or may not) have been in an examination paper when the Confuser was written, but it is not in any of the papers now (unless it has been reintroduced very recently)
If it ever was a real question, then it was probably removed following complaints form candidates. The CAA examiners are far too busy with the errors in the ATPL question bank to spend much time looking for errors in the PPL papers.
A similar current question in a current paper is as follows:
Should the oil cooler in the engine become blocked in flight, a by-pass valve allows the oil to by-pass the cooler. This by-pass valve is:
(a) temperature dependent.
(b) pressure dependent.
(c) manually selected.
(d) held open by spring pressure.
The correct answer is option b.
This question is better than the one originally posted in that it sets up a scenario in which the oil should already be warmed up, but the cooler becomes blocked. In these circumstances the pressure operated by-pass valve will open.
There is however a possibility that some candidates might interpret the scenario as one of "Oil Cooler Coring" in which very cold air over-cools the oil, making it too thick to flow freely through the filter. Based on this interpretation the candidate would then select option a.
It is important to remember that errors and ambiguities in the papers will be corrected only if examiners are made aware of them.
If you see an ambiguous question in your exam make a complaint to your examiner. He/she can then take the matter up with the CAA.