All of the following are types of gestalt grouping principles described by gestalt psychologists, except a. proximity b. closure c. similarity d. figure and ground

The answer is D. figure and ground
Proximity refers to grouping principles which states objects withclose shapes will appear as group if being palced close to each other. Closure refers to our tendency to complete a figure when we see it in incomplete form.
Similarity refers to seeing something that resembles each other will lead our grouping perception.

Okay, biology isn't exactly my strongest subject (it never has been), but i'm pretty sure the answer is nucleotides. dna is made up of nucleotides. each nucleotide contains a phosphate group, a sugar group, and a nitrogen base. there are four different nitrogen bases: adenine (a), thymine (t), guanine (g), and cytosine (c). a always pairs with t, and g always pairs with c.