<u>Answer:</u> A. Tissues
<em>Cells that perform similar functions combine to form tissues.
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<u>Explanation:</u>
Cells are the smallest units in the body of an organism. Based on number of cells in an organism’s body they can be classified as unicellular or <em>multicellular organisms</em>.
It is the group of cells performing similar functions that form a tissue. Group of tissues performing similar function forms an organ. <em>Tissue structure and function may differ in plants and animals. </em>
Animal tissues are classified into four. They are epithelial tissue, connective tissue, nervous tissue and muscle tissue. In plants there are three tissue systems namely the <em>epidermis, vascular tissue and the ground tissue.
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Here are the steps;
step 1. The activated myosin head binds to actin, forming a cross bridge.
Step 2. ADP is released and myosin slides the thin filament toward the center of the sarcomere.
step 3. ATP binds to the myosin head and detaches it from actin
step 4. ATP is hydrolyzed to ADP and P(i) and the energy released re-elevates the myosin head.
