Where are growth rings in trees most visible, thus making the use of dendrochronology most applicable? in tropical zones in desert areas in temperate zones in polar areas?

Growth rings in trees are most visible in temperate zones.  Growth rings which also called as tree rings or annual rings can be perceived in horizontal cross section cut through the trunk of the tree. It is the outcome of the new growth in the vascular cambium which is a layer of cells near in the bark that is categorized as a lateral meristem. The rings are more perceptible in temperate zones where the seasons vary more markedly. The inside ration of the growth ring is shaped primary in the developing season when growth is relatively rapid, hence the wood is less dense and is known as early wood or called as the spring wood or late spring wood. The outside ration is the late wood and has occasionally been called as summer wood regularly being made in the summer however sometimes in the autumn and is denser. 

343^x = 49^4-xx = 4-xx+x=42x = 4x = 4/2x = 2therefore x = 2