Which is a noncommercial way of introducing nonnative organisms into aquatic systems? a. cargo ship hulls
b. recreational boats
c. imported used cars
d. home aquariums
e. fishing boats

Answer moral guide 

Psychologists often talk of the magical number "7" - so it is generally assumed that we can keep 7 (more or less, so 5-9 is the correct answer) items in our short term memory - we know this as a result of many experiments.

we can increase this by chunking, so for example "7 8 9 5 3" is harder to remember than "78 95 3" - try it yourself!

the answer is a)