$Which of the following cannot be made by u\sin g Williamson\text{'}s synthesis?$

In Williamson's synthesis, best results obtained if the alkyl halide is $1°$, in case of $2°$ alkyl halide, elimination competes over substitution. If a $3°$ alkyl. Halide is used, an alkene is the major product and no ether is formed.

Considering fourth option as di-tert butyl ether. It cannot be prepared by the method as it require $3°$ halide which give elimination product.

Diphenyl ether is also not prepared by the same method as there is resonance between the unshared pair of electrons of halogen and benzene ring.