why can technicians only charge used cfc, hcfc, or hfc refrigerant back into the evacuated appliance or into another appliance owned by the same owner

The rock in a lead ore deposit contains 89 % pbs by mass. how many kilograms of the rock must be processed to obtain 1.5 kg of pb?

According to the tide table below what time of day will the highest tide occur?

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