What is the most likely reason that the steam locomotive was developed soon after the steamboat?

What is the most likely reason that the steam locomotive was developed soon after the steamboat?

a. The steamboat was useful only for transporting goods, not people.
b. The locomotive used the same technology but could travel more broadly.
c. The steamboat was practical only in England, which is an island.
d. The locomotive used more efficient technology and was less expensive.