B. Thick Atmosphere
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Excitation-contraction coupling refers to the series of events that begins with the excitation of the sarcolemma in response to stimulation by a neurotransmitter, and results in the release of calcium ions from the sarcoplasmic reticulum.
Hence, option D is the 1st process that starts the excitation-contraction coupling.
The answer would be:
B. Sequence of the bases in DNA molecules.
Here is more about your questions:
DNA contain the instructions of the traits of an organism. Most of the organism have the same DNA but what makes each different is the sequence of the DNA. The sequence gives the instructions for the production of amino acid that will produce, which in turn determines what traits will be passed on or manifested by that individual.
I believe it would be an observation
Observation in scientific process refers to gathering facts and information. In this particular context, we could see that the microbiologist is simply stating what he/she saw on the mold on the agar plate. The microbiologist simply writing down all the facts without making any explanation or assumption.
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