Ether (a) has the most hindered oxygen
Ether(b) has a less hindered oxygen
Ether (c) has the least hindered oxygen
Ether (d) lacks any hydrogen at the α-carbons

Ether (a) forms the most stable radical
Ether(b) forms a less stable radical
Ether (c) forms the least stable radical
The lone pairs of oxygen in ether (d) are in conjugation with the phenyl groups

Ether (a) forms the most stable radical
Ether(b) forms a less stable radical
Ether (c) forms the least stable radical
Ether (d) lacks any hydrogen at the α-carbons

None of these