How has physical geography blocked permanent settlement in antarctica?

a. constant snowfall prevents people from farming.
b. the ocean surrounding antarctica is always frozen.
c. ice sheets make it hard for people to meet their needs.
d. people could find a passage through the coastal mountains.

! i have been stuck on this question forever!

Donald is studying the eating habits of all students attending his school. he samples the population by dividing the students into groups by grade level and randomly selecting a proportionate number of students from each group. he then collects data from the sample. which type of sampling is used? select the correct answer below: systematic sampling convenience sampling stratified sampling cluster sampling