Hello,
In lines 48 - 52, since they’re trying to account for Mars - an unlikely source for shergottites, by comparing the absence of lunar meteorites on Earth, I inferred a Block of 4 from line 51.
Moon 
smaller size + closer to Earth
Mars larger size + farther from Earth
Basis this, I also chose the Option II for Q21 which was wrong. I’m trying to understand if I read too much into the text and incorrectly interpreted a Block of 4 that doesn’t exist? Also, when they talk about Moon’s smaller size and closer proximity to Earth, what are they stating this in relation to - isn’t it Mars only?
Thank you.