Answer:
A cell wall
Explanation:
Plant cells are enclosed by a rigid cell wall. When the plant cell is placed in a hypotonic solution , it takes up water by osmosis and starts to swell, but the cell wall prevents it from bursting.
Diluting an acid decreases the concentration of H+(aq) ions , which increases the pH level of the solution towards 7 , making it less acidic . However , the pH level of an acidic solution cannot become greater than 7 , because the water you add to dilute it is not alkaline .
-10grade/week
Explanation:
Given parameters:
Initial grade = 95grade
Final grade = 65grade
Time = 3weeks
Unknown parameter:
Rate of change of grade = ?
Solution:
Rate is defined as the change of a quantity with time.
Rate of change of grade = 
Rate of change of grade =
= 
Rate of change of grade = -10grade/week
The rate of change of the student's grade is -10grade/week. It implies that the grade of the student reduces by 10unit per week.