the parity bit is the last bit of every byte, and aims to balance the number of 1s in every byte to be odd/even. this can be used to error check a byte, because if you know the number of 1s should be even for example, yet the byte has an odd number of 1s, then we know some of the bits of the byte have been scrambled and the byte must thus be corrupted.
we can notice that the first byte has odd parity, second has even, third has even. because the second and third bytes have different parity to the first, we can assume that the parity is meant to be odd and that the second and third bytes are corrupt. tbh the question doesn’t consider that corruption of data can still maintain parity, but in the context of hsc i guess you can assume that any corrupted data would have a different parity to what it’s meant to be.