Which needle size is most commonly used for routine venipunctures?

21 is the most common needle gauge used for routine venipuncture. This gauge needle is used to draw blood for testing.

Pretty bad i would assume.

You did not show us the image of the burger, but i shall try to answer as best i can.  when purchasing food, always consider the ingredients as well as the person who prepared it. consider if they were hygienic people or not, in case the burger was infected with bacteria. no mortal should place an infected burger into their mouth.