Question

After a fetus has developed for three months, what is its skeleton made of?

Muscle

Bone

Cartilage

Tendon

Answer 1

CArtilage

Answer 2

Muscle and tendon are generally not considered to be part of the skeleton; therefore, the answers are narrowed down to either cartilage or bone.
A timetable of the formation of bones in the human body can be found at http://en.wikipedia.org/wiki/Ossification
see also http://en.wikipedia.org/wiki/Bone#Formation
According to the Wikipedia articles, bones form where there is pre-existing connective tissue (cartilage), and bone formation begins during the third month of fetal development, but some bones don't form fully until after birth.
More general information about fetal development can be found at
http://www.nlm.nih.gov/medlineplus/ency/article/002398.htm

Answer 3

cartilage