What are the complimentary base pairs of dna

Mercury metal is poured into a graduated cylinder that holds exactly 22.5 ml the mercury used to fill the cylinder mass in 306.0 g from this information calculate the density of mercury

Which correctly describes crossing over ?

The graph shows the area of forest cover in various regions of the world through a forest station forest habitats have been established in areas that previously didn't have forest and with geographic region has this approach been most successful