Scientists at the Los Alamos National Laboratory

[JbhB682]

Hi Sage -- why cant B be interpreted in this format (X and Y markers listed below)



Scientists at the Los Alamos National Laboratory have succeeded for the first time in mining heat from the Earth’s interior and producing enough energy on a commercial scale

for electricity to be generated efficiently ( = X marker)

and

to heat factories and homes. ( = Y marker)

X and Y markers are prepositional phrases hence grammatically similar in terms of structure

[Sage Pearce-Higgins]

I guess, in simple grammatical terms, that you could analyze the parallelism in that way. It seems to be fine. However, the sentence is not very clear: we might easily get mixed up with the parallel elements. Notice how answer D repeats the word 'for' to make clear what the parallel elements are (hint: learn from correct official answers). Of course, answer B can be eliminated for the meaning problem at the start of the sentence: the connection between the 'mining' and the 'producing' isn't clear.