The principle states that whoever asserts a claim before a court must prove it. Here, A approaches the court and asserts that B, C and D committed a specific crime, asking the court to punish them for it. The question is what exactly A's burden of proof covers.
Applying the principle strictly to who is doing the asserting, the burden of proof stays with A, and it covers exactly what A has claimed, that B, C and D committed the crime.
Therefore, the correct answer is A must prove that B, C and D have committed the crime.
Every question in this set turns on one moving part in the facts, so it helps to isolate that part first before checking the options against it. Here the principle ties the burden of proof to whoever is making the assertion before the court, and the only party doing any asserting is A, who has gone to court claiming that B, C and D committed a particular crime.
Running each option through the single question of who is asserting what leaves only one answer standing, the burden sits with A and covers the full claim A has made.
Therefore, the correct answer is A must prove that B, C and D have committed the crime.