Explain why you cannot draw a conclusion about the effect of one variable in an investigation when the other variables are NOT controlled.

Because you don't know which variable caused the effect.

Explanation:

It's always important to have a control because you need to be able to pinpoint exactly what variable caused the specific effect to take place. This is also why multiple variables can not be tested at once.

you go to account and hit delete!

explanation:

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.