Which pair of forces do scientists believe are responsible for tectonic plate motion? A. gravity acting on the edges of plates and convection in the mantle

B. gravity acting on the edges of plates and friction between the plate and the asthenosphere

C. friction between the plate and the asthenosphere and pressure of magma on the edge of the plate

D. convection in the mantle and pressure of magma on the edge of the plate

Freezing meltingand evaporation

Ifound the exercise on the internet. attached is the list mentioned above.in order for a compound to be considered optically active it can't have any axis or plan of symmetry. the molecule  shouldn't also  be superimposable on its mirror image.with such considerations, the compounds that are optically active are: -third compound on the first image is optically active; -second and third compound from the second image are optically actives.