The last two answer choices are Crossing over introduces variety in nature by creating new types of genes.

Crossing over maintains the count of genes and the original alleles in both chromosomes.

the second type of galaxy is called a barred spiral, which has a thing called a bar straddling the nucleus

the rocks are classified by the geological process they are formed by. the three main groups of rocks are igneous, metamorphic, and sedimentary. minerals are not they are classified under the chemical classes they are in. these groups include silicates, sulfates and carbonates.