Why is being heterozygous for sickle cell anemia considered an advantage?​

What is the difference between how ionic and covalent bonds form

When wind creates a sand dune, the sheltered side of the dune is less steeply sloped than the windward side has the same incline as the windward side is more steeply sloped than the windward side

The image shows a sandstone formation with visible bands of different colors. what do the bands indicate about how this sedimentary rock was formed? choose two answers. a). the rock was made from more than one material. b). water was absent during the compaction and cementation process. c). sediments and other matter were deposited in layers before lithification. d). the rock was stretched horizontally by the pressure from surrounding rocks. e). layers of hot liquid in the rocks cooled and solidified at different tempatures