PLZZZ HURRY Stuart designed and built a water filter in class. He wants to know if it will make water from lakes or streams safe to drink. Which of
the following would it be best for Stuart to measure in an experiment in order to test his design and answer this question?
А. the amount of time required for different volumes of water to pass through his filter
В. the diameter of the largest grain of dust, dirt, or sand that can pass through his filter
C. the amount of bacteria and impurities in water both before and after it passes through his filter
D. the maximum force that can be applied to his filter without breaking it

C! The amount of bacteria and impurities in water both before and after it passes through his filter!

Explanation:

Although each of these properties of Stuart's filter may be worth testing, the one that will tell him whether his filter can make lake water safe to drink is the amount of bacteria, parasites, and impurities in water both before and after it passes through his filter. Some filters are good at removing impurities, but not bacteria. Other ways of purifying water may kill bacteria but not remove impurities.

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.