Without further context I would assume the answer here is: Hydroxyl groups.
Positioning the child on the side (side-lying position) is the priority action after tonsiloectomy. It will permit the flow of secretions (like blood) from the mouth that could block the child's airway (airway patency is the priority). So, the most important thing is to maintain an open airway. Excessive coughing could actually trigger bleeding. The child will be on nothing-by-mouth status during the immediate postoperative period.
Every type of cell is capable of regeneration from bacteria to humans to animals.
From the given choices, the first that would be deposited by the river is the sand. This is because sand are comparatively smaller than all of the given substances. This makes it easier for river to transport it and deposit it.
The evolution of cells with nuclei and organelles
