When coming to building something, some materials are more vulnerable to water and can wear away easier. Some can keep the water in, so depending on the material, the water quality can be better sustained.
The correct option is C.
Obligate anaerobes are micro organisms that are poisoned and killed when exposed to the normal atmospheric oxygen concentration. These organisms can only survive in the absences of oxygen, therefore, they carry out only anaerobic form of respiration in order to obtain the energy that they need. <span />
Depending on what trait the alleles carry, the brothers will have a different phenotype and a different genotype.
For example; Eye color. My sister is heterozygous, meaning she has brown eyes. I am homozygous recessive, meaning I have blue(green/hazel) eyes. We both have the same parents, I just happened to inherit both of the recessive eye color alleles from my parents whereas, my sister inherited both the dominant and recessive alleles.
So, since the brothers inherited different sets of alleles, their genotype for a certain trait will be different.
Star brightness is defined by either <span>D. apparent magnitude - when we measure it from Earth (that is how bright it is from Earth) - this is the closest to "basic observation" and the best answer
or by absolute magnitute - how bright it would be at a certain distance (this allows to compare the brightness).
</span>
