The correct answer to this question is C) 94%.
CALCULATION:
As per the question, the work put into a lever is 930 Joule.
Hence, input work W = 930 Joule.
Work accomplished by the lever is 870 Joule.
Hence, the output work W' = 870 Joule.
We are asked to calculate the efficiency of the level.
The efficiency of the lever is defined as the ratio of output work to the input work.
Mathematically efficiency 


In percentage, efficiency 

[ans]
Hence, the efficiency of the lever is 94%.