The dissociation reaction of acetic acid is as follows:

The acid dissociation constant K_{a} is
.
Let the initial concentration of acid be A, and concentration of
and
be zero.
After dissociation, concentration of acid becomes A-x and that of both
and
becomes x.
Expression for acid dissociation constant will be:
![K_{a}=\frac{[CH_{3}COO^{-}][H^{+}]}{[CH_{3}COOH]}](https://tex.z-dn.net/?f=K_%7Ba%7D%3D%5Cfrac%7B%5BCH_%7B3%7DCOO%5E%7B-%7D%5D%5BH%5E%7B%2B%7D%5D%7D%7B%5BCH_%7B3%7DCOOH%5D%7D)
pH of solution is 3.5, thus, concentration of hydrogen ion can be calculated as follows:
![pH=-log[H^{+}]](https://tex.z-dn.net/?f=pH%3D-log%5BH%5E%7B%2B%7D%5D)
On rearranging,
![[H^{+}]=10^{-pH}=10^{-3.5}=0.0003162](https://tex.z-dn.net/?f=%5BH%5E%7B%2B%7D%5D%3D10%5E%7B-pH%7D%3D10%5E%7B-3.5%7D%3D0.0003162)
Since,
Thus,
![[CH_{3}COO^{-}]=0.0003162](https://tex.z-dn.net/?f=%5BCH_%7B3%7DCOO%5E%7B-%7D%5D%3D0.0003162)
and, 
Putting the values, in expression for acid dissociation constant,
![1.76\times 10^{-5}=\frac{(0.0003162)(0.0003162)}{[CH_{3}COOH]_{initial}-0.0003162}](https://tex.z-dn.net/?f=1.76%5Ctimes%2010%5E%7B-5%7D%3D%5Cfrac%7B%280.0003162%29%280.0003162%29%7D%7B%5BCH_%7B3%7DCOOH%5D_%7Binitial%7D-0.0003162%7D)
On rearranging,
![[CH_{3}COOH]_{initial}=\frac{(0.0003162)\times (0.0003162)}{1.76\times 10^{-5}}+0.0003162=0.006](https://tex.z-dn.net/?f=%5BCH_%7B3%7DCOOH%5D_%7Binitial%7D%3D%5Cfrac%7B%280.0003162%29%5Ctimes%20%280.0003162%29%7D%7B1.76%5Ctimes%2010%5E%7B-5%7D%7D%2B0.0003162%3D0.006)
The corresponding value that is the least precise would be A. As it only contains 1 value that is a significant digit, 1.
The answer is B. It will grow towards the hole in the box because the plant will try and get as close to the sunlight as possible which is called phototropism.
The answer is cells
The answer is cells