Europa, an ice-covered moon of Jupiter also believed to have a subsurface ocean, might have water vapor jets spewing into space as well, similar to Enceladus. The Hubble Space Telescope has seen what looks to be vapor jets bubbling on Europa.

Which two words could BEST replace "subsurface" and "spewing" in the paragraph above?
a.congested; regurgitating
b.concealed; cascading
c.subterranean; erupting
d.subpar; churning