Blood moving through veins can only flow in one direction because of the vein's

valves
pressure
contraction
restrictions

The intervention of extraterrestrials has been used to explain the bermuda triangle, a region of the atlantic ocean where ships and planes are frequently lost, leaving no evidence behind. how would this explanation best be characterized?

Which of the following is a common response to cell signaling?

This connective tissue consists of large round densely packed cells with the nucleus pushed to one side.