Answer:
B
Explanation:
Fathers and sons are beginning to have different ideas about what marriage is
Each guide was helpful, but we forgot to thank them.
You should use the plural pronoun, because we don't know whether the guides were only males, or females, or whether there were both sexes.
Answer:
but much research has been done and more has learned about brain injuries in the last 5 years
Explanation:
because this shows they are telling more players about the injuries and informing them about the dangers of playing
