The same three command words recur across all three parts, and each demands a different depth of answer — using the wrong depth for the word given is one of the most common ways marks are lost.
What each command word actually demands
Word
What it demands
Where it appears
Describe
State WHAT is shown — the pattern, the location, the trend — with evidence, but no reasons required yet.
Part (a), most years
Explain
State WHY — the mechanism or cause behind the pattern or challenge, referencing both the geography and the evidence.
Part (b), most years
Evaluate
WEIGH options or impacts against a stated criterion and reach a justified judgement — the only command word that requires you to actually decide something.
Part (c), every year
✓
The verb changes even within "the same" question type
Part (a) has appeared as "describe" (2022, 2023) and also as a "why is this important" question (2023's "why is flooding an important issue") — which is closer to explain. Always match your answer's DEPTH to the actual verb printed in front of you that year, not to what part (a) usually asks.