Which of the following is methanide?

Methanides are ionic carbides that contains discreate carbon atoms in the form of C^4- and given methane on hydrolysis.

Hydrolysis of Be₂C is:

${\mathrm{Be}}_2\mathrm{C}+4{\mathrm{H}}_2\mathrm{O}\to 2\mathrm{Be}{\left(\mathrm{OH}\right)}_2+{\mathrm{CH}}_4$

Hydrolysis of CaC₂ is:

${\mathrm{CaC}}_2+2{\mathrm{H}}_2\mathrm{O}\to \mathrm{Ca}{\left(\mathrm{OH}\right)}_2+{\mathrm{C}}_2{\mathrm{H}}_2$

Hydrolysis of SrC₂ is:

${\mathrm{SrC}}_2+2{\mathrm{H}}_2\mathrm{O}\to \mathrm{Sr}{\left(\mathrm{OH}\right)}_2+{\mathrm{C}}_2{\mathrm{H}}_2$

Hydrolysis of Mg₂C₃ is:

${\mathrm{Mg}}_2{\mathrm{C}}_3+4{\mathrm{H}}_2\mathrm{O}\to 2\mathrm{Mg}{\left(\mathrm{OH}\right)}_2+\mathrm{HC}\equiv \mathrm{C}-{\mathrm{CH}}_3$

Hence, Be₂C is a methanide.