Black to move
Probably best for Black is
6...exd4
[ 6...Na5
is another move which deals with the dual threats of Qb3 and Ng5.]
7.cxd4
[ 7.Ng5
Ne5
]
7...d5
8.exd5
Na5
This is an example of recognizing and dealing with threats. In order to progress in chess one must be able to do this.