Often has different layer, the layers can be straight or curvey.
Colors of the rock come in a huge variety.
Usally contain fossial. :)
First, what is a nebula?
A nebula is a cloud of dust or different elements (remember, the Space is to a big extent empty)
A planetary Nebula is a kind of nebula that is specifically formed with ionized gas that was released and surrounds a red giant star.
Answer:
I will recommend the Tifway 419 due to it's strength, density and attractive colour. In addition to that Tifway 419 has resistance towards frost and in case of weariness it can quickly recover. Morover it grows in early spring.
I'm guessing that the answer is droughts? i'm not really sure...