Suppose that vector c = a - b . under what circumstances is the length of c equal to the sum of the lengths of a and b?
1-when a and b are parallel
2-when a and b are in opposite direction
3-always
4-never

The chemical effect of the endocrine system is longer lasting than the chemical effect of the nervous system. select the best answer from the choices provided t f

What is the earliest point in the universe that we can observe? why can’t we see back further than this?

Astudent creates a model of a closed ecosystem by filling a glass tank half full with water, then adding 10 snails and two small aquatic plants. the next day, all the snails are dead. what is the most likely cause of their death?