The composition of the cerebrospinal fluid is similar to extracellular fluid with the exception of

Calcium

Calcium is known to be most abundant mineral present in the body  and they can be found in some foods and available in dietary supplements, resent in some medicine such as antacids. Also, calcium is required for muscle function,intracellular signaling, vascular contraction, hormonal secretion and nerve transmission.

humans, along with other animals and plants, have linear chromosomes that are arranged in pairs within the nucleus of the cell. the only human cells that do not contain pairs of chromosomes are reproductive cells, or gametes, which carry just one copy of each chromosome.

i think that d. wind is the answer.   i missed the question when i answered a. currents.