The pronoun "who" should be replaced with "whom" in the following sentences:
- The water from the faucet has turned brown, but I'm not sure whom to call about it.
- Who do you think should be the next president of the science club? should be changed to Whom do you think should be the next president of the science club?
So, the correct sentences that should use "whom" instead of "who" are:
- The water from the faucet has turned brown, but I'm not sure whom to call about it.
- Whom do you think should be the next president of the science club?