Answer the following question given this paragraph: 

Sending humans to the seafloor is expensive and dangerous. Having to return humans safely to the surface limits what a mission can do. Remotely operated vehicles , or ROVs, allow scientists to study the deep without going to the seafloor. These small vehicles carry cameras and scientific instruments. ROVs were used to study inside the Titanic . This would have been far too dangerous for a manned sub to enter. Scientists control ROVs electronically with sophisticated operating systems.


Q: What do scientists use to study the deep without going to the seafloor?


A:
remotely operated vehicles