In the picture attached to this question, the two diagrams above did not show very well but I believe that the first diagram contain four dots, which means that the correct option is A.
Carbon has six electrons, that is why 6 is its atomic number is 6 . In writing electronic configuration, two electrons are usually placed in the most inner shell while the other shells will have 8 electrons each. In the case of carbon which has 6 electrons, only four will remain after 2 electron has been put in its inner shell. Therefore the number of electron in its outermost shell will be four.
Because human DNA is so very long (with up to 80 million base pairs in a chromosome) it unzips at multiple places along its length so that the replication process is going on simultaneously and more accurately.
B temperature and precipitation
