Ilana is having a baby and it is only three and a half weeks since conception. at this stage, which central nervous system structure(s) will have begun to form?

Neural tube

Explanation: Central nervous system originates from ectoderm, neuroectoderm gives rise to neural tube, the primordia of brain and spinal cord. Neural tube is the embryonic structure, neural plate folds into neural tube is formed at the dorsal side of embryo.

do you have a picture?

one part of the electromagnetic spectrum that arrives on earth as solar radiation from the sun is the visible spectrum. wavelengths of the visible spectrum combine to form what we refer to as

answer - d) ultraviolet radiation.

violet /   380–450 nm / 668–789 thz

violet is number 1 in the chart of visible light.