Balance the following equation:
SiO2+HF →SiF4 +Н2 O

c- cold periods in earth's history during which glaciers covered much of the surface.

explanation:

under a microscope, cancer cells may look very different from normal cells. they often have different sizes and some may be larger than normal while others are smaller. cancer cells are often abnormally shaped and the control centre of the cell (the nucleus) may have an abnormal appearance.

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