Fuel cell, using hydrogen and oxygen as fuels,

A. has been used in spaceship

B. has as efficiency of $$40 \%$$ to produce electricity

C. uses aluminum as catalysts

D. is eco-friendly

E. is actually a type of Galvanic cell only

Choose the correct answer from the options given below:

Match List I with List II

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If an iron (III) complex with the formula $$\left[\mathrm{Fe}\left(\mathrm{NH}_3\right)_x(\mathrm{CN})_y\right]^-$$ has no electron in its $$e_g$$ orbital, then the value of $$x+y$$ is

The number of unpaired d-electrons in $$\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+}$$ is ________.