What elements are in the most common substance in the human body? A. Carbon and nitrogen
B. Hydrogen and oxygen
C. Oxygen and phosphorus
D. Calcium and nitrogen

The four most abundant elements in the human body – hydrogen, oxygen, carbon and nitrogen – account for more than 99 per cent of the atoms inside you. They are found throughout your body, mostly as water but also as components of biomolecules such as proteins, fats, DNA and carbohydrates.

vascular tissue transports materials from the environment into the plant.

your answer is "the 1950's"