On a sunny day mark can stay in the sun for 20 minutes before he gets sunburnt. he wants to sunbathe for 3 hours. what is the lowest level of sun protection that he should use : 5, 15, 20, 30, 50
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primary succession begins with a bare rock and ends with a forest secondary succession begins after a natural disaster where there is a temporary setback after a forest fire or local destruction, but the surrounding area can fill in

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.