Question 6
Beyond the main four, which set of elements is essential to a living body in smaller amounts?
The right answer is the one marked above.
Sulphur, phosphorus, sodium, potassium, calcium, magnesium, iron and chlorine. A body cannot survive without them, even though it needs far less of each than of the main four.
Calcium alone is about 1.5% of body mass, phosphorus 1%, potassium 0.35%, sulphur 0.25%, sodium 0.15% and magnesium 0.05%. Chlorine, iron and iodine are present only in traces — and a shortage of any of them still shows.