Respuesta :
What Andrea should be doing if she wants to improve her flexibility and is already doing certain strength-building exercises together with flexibility ones, then adding additional weightlifting exercises will not be that helpful, neither will be biking as biking doesn't really incraese neither muscle mass used for flexibility nor does it improve flexibility.
I believe the answer is: biking
When you are biking, you would put your body on a certain position for a long period of time. If this being done regularly, it would reduce the flexibility of the part of body that is used to remain fixed in a place. Rather than biking, Running is a better option for Andrea's flexibility since it moves all part of her body.