Breakdown of Wer den Versuch leitet, muss hierzu einen Bericht schreiben.
ein
a, an (eine)
wer
who
schreiben
to write
müssen
to have to, must
Questions & Answers about Wer den Versuch leitet, muss hierzu einen Bericht schreiben.
Why use hierzu instead of dazu here?
Both translate to 'on this' or 'about this', but hierzu is a proximate pronominal adverb. Using hier- instead of da- makes the reference feel closer and more immediate. It emphasizes writing a report on this specific experiment at hand, rather than just a more distant 'that' one.
Why does the second clause start with the verb muss instead of a subject pronoun?
In German, the conjugated verb must always take the second position in a main clause. The entire first clause (Wer den Versuch leitet) acts as the subject and occupies position one. Therefore, the conjugated verb muss must come immediately after the comma in position two.
Why does hierzu use the preposition zu? Wouldn't you write a report 'about' (über) something?
While you can absolutely write a report 'about' something (einen Bericht über etwas schreiben), in formal, academic, or professional contexts it is very common to use zu to mean 'on' or 'regarding' a topic. So hierzu means 'regarding this', which fits perfectly for a formal experiment report.
How does Wer work at the beginning of this sentence? Is it a question word?
Here, Wer is not a question word. It is used as a relative pronoun meaning 'Whoever' or 'Anyone who'. It introduces a free relative clause, which means it doesn't describe a previously mentioned noun, but rather stands on its own to represent an unknown person.