Why does shells have ribs?

in the year 2850, humans successfully colonized mars. the martian modules that were constructed could hold only a small population of people. it is now a century later, and the population on mars has grown to 600 people. of the current mars population, 45 people express the recessive phenotype for phenylketon- uria (pku) syndrome (pp genotype).

explanation:

i do believe the correct answer would be the third one. location c, because earth is tilted away from the sun at this time

hope this

answer/// to address the needs of adults with mental illness and increase their ability to function;