Which statement about air masses and fronts is correct?
a)
only a front is the movement of a weather system.
b)
an air mass is a large body of air that takes on the characteristics of the area over which it forms, while a front is a narrow region separating two air masses of different densities.
c)
a front takes on the characteristics of the area over which it forms, while an air mass is a narrow region separating two different densities areas.

Option (B)

Explanation:

The front refers to the transition zone that lies between two types of air masses which are of distinguishable density. It extends both vertically and horizontally. The fronts are divided into 4 types, namely-

(1) Warm front

(2) Cold front

(3) Stationary front

(4) Occluded front.

These fronts are often shown in the weather map by using patterns with different colors, where each indicates a type of front.

On the other hand, air masses refer to the body of air mass that is characterized by having a certain composition of density, temperature and moisture content. It varies from place to place.

Thus, the correct answer is option (B).

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!