Of should be offered two times for use as in, "All of these books are full of dust."
you can always just type it
Covered in dust?
That's an excellent suggestion. Report it.
I didn't realise 'plein' needed a plural form; thought it worked like 'beaucoup'!
The indefinite determiner (quantifier) "plein de" works like "beaucoup de", but this is the adjective "plein(e)(s)".
I used "dusty" instead of "full of dust" and it was marked wrong. How do you say dusty?