Study the image about convection currents. at which location does heat transfer begin as dense material heats up 1 2 3 4

Heat transfer begins at 4.

Explanation:

Heat transfer is the means by which heat can be passed from one object to another. Majorly, there are three methods of heat transfer; conduction, convection and radiation.

Conduction is a method of heat transfer that majorly takes place in solids. It requires material medium for it propagation.

Convection is a method of heat transfer in fluids. Liquids and gases has molecules that are free to move from one point to another. It requires material medium for its propagation. One of its major applications is the convectional current.

Radiation is the propagation of heat within heating up the intervening medium between the source and the receiver. It does not require material medium for its propagation.

Heat transfer would begin at 4 as the dense material heats up. because it is the inner part of the material. And this part might conduct heat from neighboring parts or molecules.

the unequal cytoplasmic division that  results  in  one egg  and three polar bodies ensures that a fertilized  egg has  ample nutrients  forits journey  to  the uterus.

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds