Which of the following is an example of how a scientist might use a model? a. a wrench is used to tighten a nut onto a piece of wood b. marbles placed onto a hollow sphere are used to describe protons in a nucleus c. stopwatches measure the amount of time it takes for runners to complete a mile d. microscopes are used to magnify a group of cells on sets of slides

I do believe the answer is:D.

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.

each  column  of the  table  is called a group. elements in a group share similar properties. groups are  read  from  top  to  bottom. metal. metalloid. nonmetal. solid. liquid. gas. fe. hg. o.  2. 3. 4. 5. 6. 7. 8. 9.  2. beryllium. 9.012. 4.  sodium. 22.990.  11. 3.  magnesium. 24.305.  12.  potassium. 39.098.  19. 4.  calcium. 40.078.  20. i guess  i