Constriction occurs when the muscular walls of blood vessels contract, and dehydration causes vessels to constrict and blood to thicken. Given these facts, what causes blood to thicken among the following options:
- Constriction
 - evaporation
 - heat or cold
 - thirst
 - permineralization
 - sweating
 - flow of electrons
 - matter vibrating


 

 Constriction        