is independent of the temperature of the source and the sink
is independent of the working substance
can be $100 \%$
is not affected by the thermal capacity of the source or the sink
Solution
We know that, the efficiency of Carnot heat engine is
$
\eta=1-\frac{T_2}{T_1}
$
where, $T_1=$ temperature of source (hot reservoir) $T_2=$ temperature of sink (cold reservoir)
Hence, efficiency depends only on the temperature of hot and cold reservoir but independent of the working substance