Why is precipitation typically associated with fronts?

a. fronts have higher relative humidity than the surrounding air.
b. along fronts, warm air rises, cools, and causes water to condense.
c. the warm air draws moisture out of the cold air, which then falls as rain.
d. when warm air and cold air mix, water droplets can form and fall as rain. v

Can someone me with 3 and 4 plz. this is for masteries test.

3.09 lab: reaction of metals 1 which combinations of substances resulted in a chemical change? for each metal that participated in a chemical change, write the type of metal it is, based on your examination of the periodic table. were there any metallic compounds that did not react with either the acid or the base? write the type of metal, based on your examination of the periodic table. make a general statement about the reactivity of the metals in this experiment.

#7 how does the structure of amino acids allow them to form a polypeptide? each amino acid has an amino group and a carboxyl group. each amino acid has a hydrogen atom and a carboxyl group. each amino acid has a carboxyl group and an r group. each amino acid has an r group and a hydrogen atom.