The work done by static friction can be : a. zero
b. negative
c. positive
d. any of the above

A. Zero

Explanation:

The definition of work is related with the energy that a force 'F' implies in a displacement 'Δx'; it means that it is necessary that the body which is over the force comes under a displacement to develop work. The static friction is a force which is only present when there is no movement; when a force overcome the static friction force, the dynamic friction force appears and it is said that the static one disappear. In that sense, the static friction won't ever be a force that can induce a displacement, so the work done by this force will always be zero.

the cellphone, they would then know if the killer would have contacted them or always hated them. or if it was a breakup. but if that is not the case, then it would be the clothing. to put in a bullet, it would have to be put in by hands. hands have finger prints which, would have giving you the answer of who done it.

explanation:

absorption lines are where light has been absorbed by the atom thus you see a dip in the spectrum whereas.

emission spectra have spikes in the spectra due to atoms releasing photons at those wavelengths.

explanation: