Scientists at the Los Alamos National Laboratory have

Kindly let me know if the idiom rule applies to highlighted part

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.

I feel the parallelism should occur in this part of setence also..There (C) does not hold good.Pls explain the answer

You mean D...

following idiom can found in A and B .. but they are not logically good.
Succes in X and Y ..(
succeeded ... in mining...(X) AND Producing ..(Y)...
---> this means succeeded for fist time in X and succeeded for fist time in Y( Producing energy on commercial scale..this is wrong.. "producing energy commercial scale.. may already succeded by other methods too...)

succeded for first time in mining heat... to produce energy on comerical scale( this is what they succeeded first time)

Somhow I didn't checked the idiom -
Answer E

Sentence has parallel issue – Scientists at … have succeeded … and producing …
Eliminate A, B and C

A. and producing energy on a commercial scale, enough for efficient generation of electricity and heating [have succeeded … and producing … - not parallel – eliminate it]
B. and producing enough energy on a commercial scale for electricity to be generated efficiently and to heat [have succeeded … and producing … - not parallel – eliminate it]
C. for energy production on a commercial scale, enough for generating electricity efficiently and to heat [have succeeded … for production … - not parallel – eliminate it]
D. to produce energy on a commercial scale, enough for generating electricity efficiently and for heating [enough modifying incorrectly – for generating – eliminate it]
E. to produce enough energy on a commercial scale for efficient generation of electricity and heat [Hold it]