According to the author, the impracticability of using coal, oil shale and coal tars as sources of energy is due to ___________ . A. their being time consuming B. their being money consuming
32/40
According to the author, the impracticability of using coal, oil shale and coal tars as sources
of energy is due to ___________ .
their being time consuming
their being money consuming
the scarcity of sources
the lack of technology their being money consuming