Four boys in the class sent a valentine to a different girl. henry didn’t send one to annabel, but billy sent one to either mary or deborah. mary didn’t get a card from john or greg. neither john nor greg sent a card to harriet. greg would never send a card to annabel! who sent a valentine to annabel?

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.

d) 48

step-by-step explanation:

16,32,48,64,80,96,112,128,144,160,176,192,208,224,240,256,272,288,304,320,336