Answer:
The answer to your question is the letter A. Cells
Step-by-step explanation:
A. Cells this choice is the correct answer because a tissue is many cells interconnected that perform a similar function.
B. Water this choice is incorrect because do not form part of this level of organization of living things.
C. Bacteria is a living thing, a prokaryotic cell, many bacteria do not form tissues, so this choice is incorrect.
D. Protons are a level of organization that comes before cells and molecules, not before tissues, so this choice is incorrect.