Two pens in a pencil case on the couch how to speak English

Oxalic acid is used to reduce ferric tannins so that it dissolves in water and ink traces can be washed off clothes.

The blue ink can be removed, didn't I buy a board of gel pens when I was in school, and there was a pen in it that was designed to correct our writing mistakes, and when I painted with that pen, the blue pen couldn't write. Do you have an impression? Go out and buy a board and that will do the trick.

My pen isn't on the sofa.

You're a little too sensitive. Generally, clothes will be stained on other clothes when they are wet. Dry clothes and leave them there for a while, and you'll be fine.

Two cats are on the sofa,Two cats are staying on the sofa.