"linkage" refers to genes for different traits

1. forming dominate traits
2. resulting in incomplete dominance
3. being located on the same chromosome
4. being located on paired chromosomes

"Linkage" refers to genes for different traits   being located on the same chromosome

Explanation:

When two genes of different traits are located on the same chromosome they are said to be linked and their inheritance pattern is referred to as Linkage.Linked genes tend to stay together during the formation of gametes.The transmission pattern of linked genes can be complete or incomplete.Complete linkage produces 0% recombinants while incomplete linkage produces  about 50% or more recombinants.

Its either a) or b),wind and water erosion gradually widen the canyon

Plants, sunlight, growth and artificial sunlight