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A membrane that only "lets" certain molecules in while keeping other molecules out is ___ ___.
A) Flexible
B)Bilipid layers
C) Endoplasmic Reticulum (ER)

i think the answer is g1

hope i

-lavira: )

answer: accepted answer: aquatic animals use the oxygen dissolved in water to carry out respiration. since the amount of dissolved oxygen in water is low as compared to the amount of oxygen in the air, therefore the rate of breathing in aquatic animals is much faster than it is in terrestrial animals.

explanation:

the correct answer is 4) heat and pressure

metamorphic rocks arise from transformation of existing rocks types, in a process called metamorphism. during metamorphism the original rock(prolith) change into metamorphic rock by heating (150-200c) and pressure of more than 1000 bar. the original rock can be sedimentary, igneous, or existing metamorphic rock.

the correct answer is 2 and 4