The Wankel rotary engine was an engineering marvel that (i) automobile exhaust emissions, but because it was less fuel efficient than the standard piston-cylinder engine, it was (ii) in the early 1970s when (iii) pollution gave way to panic over fuel shortages.
Blank (i)
depended totally on
preceded the problems with
substantially reduced
Blank (ii)
necessitated
conceived
abandoned
Blank (iii)
ignorance of
espousal of
preoccupation with