The sentence is correct
Polluted rivers, which can exist anywhere, are unsafe for swimming.
You should watch:
Tokyo Ghouls
Kakegurui
ONE PIECE
Haikyuu
The Disastrous Life Of Saiki K (both the original and reawakened)
Dororo
The Seven Deadly Sins
HunterxHunter
The best suited for something
Answer:
I think the answer is
for first one : acknowledge counterargument that optimism ignores the fact.
second one: directly engages reader to consider why she is an optimist .
last one: establish her credibility on the topic of optimism.