What did Germany do to encourage Austria to go to war with Serbia?

AGermany promised support to Austria.
CGermany sent a false letter to the Austrian government informing them of an attack on Austria by Serbia.
BGermany threatened to invade Austria unless they went to war with Serbia.
DGermany accused the Serbian government of trying to assassinate Austrian government officials.

Verified Answer :

Neuron

Germany encouraged Austria to go to war with Serbia because Germany promised support to Austria - a. Austria knew that being backed by Germany they would have huge support and it would enable them and help them with a very fast conquering campaign of Serbia.