I dont see a problem with grammar, thought you can try to have about 1 comma per sentence. For example, "for last christmas for camping," you could end the sentence there with a period and take out the "for"
answered: Guest
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answered: Guest
Answer(a) the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other