[Casiopea]

Try looking at it this way,

Explain why each of these is not relevant to an accident when the rider presumably panics before they crash?

Note, there are two they's in today's English. "they", the plural subject pronoun, which agrees in plural number with the verb (e.g, They are fun), and "they", a gender-neutral singular pronoun, which is used in place of the phrases, he or she, she or he, and the combined form, s/he.

1. the rider panics before he or she crashes
2. the rider panics before she or he crashes
3. the rider panics before s/he crashes
4. the rider panics before they crash ('they' = s/he, she or he, he or she)
5. the riders panic before they crash

Note, given the singular nature of "they", it's expected the verb be singular as well, but it's not, yet. The validity of singular "they", or gender-nuetral "they" is still being debated, so rephrasing the sentence works best,

6. the rider panics before crashing.