How to remove varnish<br>Create good ventilation. Whether your sanding or using a chemical solvent, it's a good idea to have ventilation. Open windows and use fans to create cross-ventilation if you're inside.

Based on that paragraph can we conclude that this sentence is true?
Cross-ventilation can only occur when windows are closed.

Choices:
i. Yes;
ii. It's impossible to say;
iii. No;
iii.