Amino acids can be classified into two groups: and .

Explanation:

From a structural perspective, amino acids are typically composed of a carbon atom, a hydrogen atom, a carboxyl group along with an amino group and a variable group. Based on the variable group, amino acids can be classified into four categories: nonpolar, polar, negatively charged, and positively charged

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.

the answer is d p: cell, q: organ, r: organ system, s: tissue