I believe he is looking for an allele
An allele is a variant form of a gene. Some genes have a variety of different forms, which are located at the same position, or genetic locus, on a chromosomes. Humans are called diploid organisms because they have two alleles at each genetic locus, with one allele inherited from each parent.
An example of a false negative is taking an HIV test and having the test come back negative to say the patient is clean, but in reality they have HIV. Another example of a false negative is a woman taking a pregnancy test saying "not pregnant" (i.e. test is negative), but she actually is pregnant. Between those two examples, it is better to have a false negative pregnancy test because it is non life threatening.
A false positive example would be getting bad news you have cancer, when you actually don't have cancer. Another false positive example is a test saying you have a cold virus, when in actuality you don't. The first example mentioned would have the patient likely go through intense chemo treatments which would greatly affect their livelihood. The second example is a more harmless false positive as it would involve at most a flu shot if anything.
It is extremely useful for geologists, because most specimens of a given mineral are very close to the same hardness. ... So, we can conclude that not all the rocks are hard, and the hardness of rocks depends on how the atoms of the rock's minerals are bound to each other and how they are arranged.
B) the selection for different shaped beaks that best suit different niches
