Which of the following is a category of urban residents?

ethnic villagers

unmarried and childless people

the trapped

all of the above

Option D, All of the above

Explanation:

The urban population is increasing day by day and the major cause of this population growth is inflow of immigrant population from different villages, cities and country. Most of these people coming to the urban areas are either student (who are single and childless) or young people (who are also single and childless) for study purpose or for job. However, being childless and unmarried is becoming a common life style of today’s modern world.  

The people residing in these cities are mainly living there only for their jobs , whether they like it or do not like it and hence they are referred as trapped.  

Therefore, the correct answer is option D, All of the above

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!