The advantage of Proof of Elapsed Time($($PoET)$)$ instead of Proof of Work($($PoW)$)$ is _$\_$

a.$.$

PoET can often be used in a permissionless blockchain more easily than PoW

b.$.$

PoET has generally lower transaction cost

c.$.$

PoET is much secure than PoW

d.$.$

PoET is much faster than PoW