Which of he following was a significant challenge in building the panama canal

Tori is researching for her blog post about how wearing sunblock can prevent skin cancer, and she finds a page about her topic on the united states centers for disease control website at is this a reliable site for tori’s research? yes, because it is presented by a college or university no, because it is a personal opinion about the subject yes, because it is run by a governmental organization no, because it is intended to advertise a certain product