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What is the difference between
(be) covered in & (be) covered with

SenderNabil Morris GeorgePositionTeacherللمزيد ممكن زيارة موقع long man

The Longman Dictionary of Contemporary English provides an answer.

When cover means “hide or protect,” use with:
She covered the child with a blanket.
He covered his face with his hands.
The dictionary also gives an example with the preposition by: She wore a ... dress partly covered by a thin shawl.

When cover means “form a layer on a surface,” use either with or in:

The eruption of the volcano covered the town with/in fine ash.
So the preposition to use with the passive (as in your question) depends on the meaning of the word cover in the sentence.

What is the difference between moisture and humidity?
Moisture is small amounts of water that are present in the air, in a substance, or on a surface.
Humidity is the amount of water vapor in the atmosphere, usually expressed as either absolute humidity or relative humidity.
So moisture is the more general term. It can be water vapor or small amounts of (liquid) water in something or on a surface. Humidity is a type of moisture