I found the missing choices, these are: 
Cardiorespiratory endurance 
Body composition 
Flexibility 
Muscular strength
Rosalyn's area of fitness that needs to improve is MUSCULAR STRENGTH. 
Muscular strength is defined as the amount of force a muscle can produce with a single maximal effort. In Rosalyn's case, she needs to develop her arm muscles to enable her to hold her cousin's baby without feeling any fatigue.