What do the guard cells do?

The chief role of guard cells is to prevent an excess loss of water through respiration, allowing the plant to trade oxygen and carbon dioxide without becoming dehydrated. Guard cells are part of the system that maintains drought resistance in plants.

Explanation:

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.

answer: zinc is the substance which has a volume of 1.38 .

density is defined as the mass of an object per unit volume.

it can be calculated by dividing mass of a substance by its volume i.e.

si unit of density is kg per cubic meter and cgs unit of the same is gram per cubic centimeter.

now from the given data volume can be calculated by the formula .

hence, the volume of aluminium will be = which comes out to be 1.703 .

similarly, volume of zinc, chromium, and nickel will be 1.378 , 0.869 , and 0.356 respectively.