Which sentence is punctuated

correctly?

In first-period biology class we learned that,

Question

Which sentence is punctuated correctly?

In first-period biology class we learned that,

the ecosystem, is a fragile and sensitive thing.

The freshmen, were excited to hear about extra-credit opportunities in their algebra class.

Getting her license proved to be more difficult and tricky, than she thought it would be.

In order to serve students best, school districts need to ask for additional funding.

English Literature