Each a atom is adjacent to 3 b atoms. what is the a-c-b bond angle?

Using the simulation to build a system with 5 bonds. The resulting structure is called the Trigonal bipyramidal structure. The two different sites in a trigonal bipyramid are labeled as A and B in the drawing to the right. 
In this case, therefore, the bond angle A-C-B is 90 Degrees (right angle)

North atlantic current or north atlantic drift is the answer

The closer the atoms are to becoming ionic the more highly dense the negatively charged side gets.