A.
The first thing we need to assess is why the tooth has become loose.  This could be due to periodontal disease (bone loss) or the way your teeth bite together might put too much force on it.  Once we determine this we can assess your options an implant could be the best choice,  a bridge which attaches to the teeth either side of the but this depends on the strength of these teeth or a denture.
You need to have a full assessment first.