The principle to get a good experimental design is known as a principle
a. randomization
b. precision matching principle
d. max min con principle.

it´s related to his charming character.

beauty is not everything, although we can joke that girls only care about the physical or material aspect, the truth is that a real woman looks at more important things, besides intelligence and personality, there are other attitudes that make irresistible to men who are 'unattractive'.

for example develop your sense of humor.

well considering i can't see the graph, it's probably prices