what are the answers to these evolution questions?

Infinite population size, no mutation, no selection against a certain homozygous gene, random mating, no immigration/emigration

Mutations: Causes variation within and between populations.  If mutation is beneficial to the individual, it may be passed on.
Gene flow: Causes variation within population, decreases variation between population.  Can cause convergence since two populations will be able to mate with each other.
Genetic drift: Causes variation between populations, decreases variation within population.  Inter-breeding can cause divergent evolution as the population that broke off from the species will start to differentiate.
Non-random mating: Causes variation within and between populations.  Non-random mating could cause certain traits to be passed on while other traits may become rare.  This could also cause evolution due to the disuse of one trait and the dominance of the other one.
Natural selection: Causes variation within and between populations. Natural selection is the cause of evolution.  Certain individual who are unable to withstand the environmental pressures will be selected against, while the ones that prosper will start to pass on the effective trait, causing evolution.

Directional selection
Smaller individuals may have higher fitness (i.e. produce more offspring) than larger individuals. Natural selection is then directional: it favors smaller individuals and will, if the character is inherited, produce a decrease in average body size. Directional selection could, of course, also produce an evolutionary increase in body size if larger individuals had higher fitness.

Stabilizing selection
Natural selection could be stabilizing. The average members of the population, with intermediate body sizes, may have higher fitness than the extremes.

Disruptive selection
Natural selection could favor both extremes over the intermediate types. This is called disruptive selection.

Do your own homework. You'll find all these answers if you read your textbook for five minutes.