Explain whether a red apple is opaque or transparent

and why it appears red.

An apple is opaque because you can't see through it. It appears red because that is the natural colour

An opaque object is an object through which the light rays can not be passed and we can not see from that object while transparent object allows the passage of light. Hence red apple is unable to pass light, so it is a opaque object ... Hence red apple looks red because it absorbs all color except red.