27. Across Europe, there are about 400 of the new energy plants that burn thousands of metric tons of household garbage and industrial waste round the clock and, all the while, ___________ the trash into heat and electricity.
(A) converting (B) convert (C) converted (D) to convert
Across Europe, there are about 400 of the new energy plants that burnthousands of metric tons of household garbage and industrial waste round the clock and(, all the while,) _convert_ the trash into heat and electricity.