B. & C.
A is incorrect because the most complex level of organization is the organism itself, as a whole.
D is incorrect because a cell is what composes different tissues, it isn’t made of different tissues.
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B. The cell is the most basic structural unit of life. They are independent and can perform processes like excrete waste, take in nutrients etc.
C. There are so many different cell types such as muscle cells, stomach cells, bone, neurons, etc. meaning they “specialize” in one thing such as being a stomach cell.
Hope this helps!
Most likely it's A because you could change the height of the plant and that's what a independent variable is, a factor you can change in order to find out will happen, Hope this helps
Sickle hemoglobin mutation is a point mutation, bases are substitued from one another
The part of the cell that contains most of its dna is the nucleus