Geologists once thought that the molten rock known as lava was an underground remnant of Earth's earliest days, sporadically erupting through volcanoes, but they now know that it is continuously created by the heat of the radioactivity deep inside the planet.

(a) was an underground remnant of Earth's earliest days, sporadically erupting
(b) had been an underground remnant of Earth's earliest days and sporadically erupted
(c) was an underground remnant of Earth's earliest days, which sporadically erupted
(d) would be an underground remnant of Earth's earliest days that sporadically erupted
(e) was an underground remnant of Earth's earliest days, having sporadically erupted

The correct answer is (a). I fail to understand why is (b) incorrect ? I think there are two past actions in the sentence
(1) first action is "Lava had been underground remnant"
(2) second action is "Geologists thought"

Please explain.

(a) was an underground remnant of Earth's earliest days, sporadically erupting
(b) had been an underground remnant of Earth's earliest days and sporadically erupted

A is in simple past tense and and clearly explains that situation

I agree that the clause "that the molten rock known as lava was an underground remnant of Earth's earliest days" does not need to be in past perfect tense since there are not two distinct past actions. Furthermore, by using "and sporadically erupted" in the same clause, B suggests that the geologists also mistakenly believed that lava sporadically erupted through volcanoes.

Rey

Ray:

Just a quick question on the modifier 'sporadically erupting'. Is it acting here as a noun modifier modifying the noun phrase 'an underground remnant....'.

if it's a noun modifier --- are noun modifiers are free to modify the entire noun phrase?

if it's an adverbial modifier modifying the clause 'molten rock.....was an underground...' - why is that? Adverbial modifiers usually tell 'how', 'why', 'when'.
and this does not seem to be telling any of them.

thanks.

"comma -ing" phrases / clauses are typically adverbial modifiers, not noun modifiers. In this case, it's describing what the lava was doing.

_________________
Stacey Koprince
Instructor
Director of Online Community
ManhattanGMAT

Hi Stacey,

Thanks. But the OE said that:

"Moreover, the modifier "sporadically erupting through volcanoes" correctly modifies "an underground remnant of Earth's earliest days."

Looks to be different from your opinion...can you please tell what indeed is the case ?

Thanks
Mohit

Nope - it should be the whole thing. Molten rock was an underground remnant <-- sporadically erupting...

:)

_________________
Stacey Koprince
Instructor
Director of Online Community
ManhattanGMAT