36. Scientists at the Los Alamos National Laboratory have succeeded for the first time in mining heat from the Earth’s interior and producing energy on a commercial scale, enough for efficient generation of electricity and heating factories and homes.
A. and producing energy on a commercial scale, enough for efficient generation of electricity and heating
B. and producing enough energy on a commercial scale for electricity to be generated efficiently and to heat
C. for energy production on a commercial scale, enough for generating electricity efficiently and to heat
D. to produce energy on a commercial scale, enough for generating electricity efficiently and for heating
E. to produce enough energy on a commercial scale for efficient generation of electricity and heat
the answer is D
I'm quite uncomfortable with the "enough for" in answer D...any NN could help to explain the usage? thanks.
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