Question

which substance is considered a building block for all living things? hydrogen glucose carbon protein

Explanation:

Carbon is a fundamental element and a building - block for all living things as it is a key component of organic compounds essential for life processes. Proteins are made up of amino - acids which contain carbon, hydrogen, oxygen, nitrogen etc. Glucose is a sugar molecule with carbon as a main component. Hydrogen is an element but not the sole building - block of life.

Answer:

carbon