The correct option is D mucous and poisonous
There are two kinds of glands present in the skin of the frog, namely the mucus and the granular glands. The mucus glands secrete mucus which keeps the skin moist while the granular glands secrete poisonous substances which protect the frogs from its predators.
Sweat glands produce sweat and mammary glands produce milk. Both are commonly found in mammals, like humans.
Sebaceous glands produce oil which also helps to prevent the skin from becoming dry and helps conserve moisture. They are found in aves and mammals.