Why do carpenters use a screw instead of nails to join two pieces of wood?

Screws have phenomenal tensile strength which is far greater than nails. Screws build a tight adhesion between two pieces of wood.  

Nails are used for joints, because even after multiple twists the wood at the joints will remain together when nails are used. But a screw will come off after a single twist, if screws are used to hold wood at the joints.  

For any static wood work screws are better than nails because of their tensile strength.  

particle   p is an electron and particle q is a neutron

it would be b. 6co2 + 6h2o --> c6h12o6 + 6o2