Can someone me with this? ? i don't understand at all its about acids and bases

How have the greenhouse gasses increased from the year 2000 to 2018

Which are examples of how technology has advanced scientific understanding.1using hot water to sterilize medical equipment.2transplanting a human organ into another individual.3inserting genes from one sheep into another cell to make a cloneunderstanding the different structures that make up a cell.4examining microorganisms from the deepest parts of the ocean

Avariable that is not being directly tested during an experiment should be