The dots represent a bacterial infection. sal was very sick with this bacterial infection. the infection was treated with antibiotics. sal seemed to get well, but in a few weeks, she was sick again. how can this be explained using natural selection? a) the antibiotics were ineffective to this strain of bacteria. b) the stronger, more resistant bacteria survived the antibiotics and reproduced. c) the antibiotics did not kill the bacteria; it only forced them to be dormant. d) antibiotics will only kill a portion of the bacteria, no matter how much medicine sal takes.

B)The stronger, more resistant bacteria survived the antibiotics and reproduced.

americans began to notice growing differences between the northern and southern sections of the country. there were more people living in cities in the north, which made it more urban. more people lived on farms in the south, which made it more rural. while many people were farmers in the northern states, there were now other ways to make a living, such as working in mechanical cotton gins factories manufacturing cloth, tools and other goods. people in the north supported high tariffs on goods imported from europe because the extra cost encouraged people to “buy american” instead. in the southern states, planters did not like tariffs because they sold most of their production to europe and bought their tools from there as well. southerners believed the protective tariff was something that only northern factory owners keep their profits high. so the southern politicians came up with an idea. they would opt out. they would simply ignore the protective tariff. it was ‘null and void’ in south carolina. the state would not collect the taxes on goods imported into south carolina, no matter what the president said they had to do. this decision led to the nullification crisis.