How many variables should be tested at one time in a scientific investigation?

Some animals that try to adapt to climate changes eventually die due to starvation, as climate change alters the web.

Acandle’s wick is the fabric string that holds the flame, and it burns down at a constant slow pace when the candle is lit. the wick is usually surrounded by wax. which is the most important property of covalent compounds that makes them useful for making candle wax? a low boiling point a low melting point a high boiling point a high melting point

What is the value of the standard enthalpy of formation of an element in its most stable form?