Solution:

A

Explanation:
Pi = 3.141592653.....
All images are related by pi value i.e "The number of straight lines on each shape corresponds to the digits of pi."

Solution:

Not sure.

John Brunner always sneezes before the rain, but it was not mentioned that if Brunner sneezes, it will rain.

Solution:

Wednesday

Explanation :
There is two way to interpret this.
A) If x + 1 ==> x - 1
Then
x ==> x - 2
x - 2 = Friday
x = Sunday

B)If x - 1 ==> x + 1
Then
x ==> x + 2
x + 2 = Friday
x = Wednesday

Option B) makes sense and hence the answer.

Solution:

In a clock.

Explanation:
time is 12 hour 10 minutes (here by looking at 2, we say 10 minutes)

Solution:

Tank-5

Explanation:
This is a variation of Which Tank Will Fill First Brain Teaser but in this puzzle connection between tank-5 and tank-2 is closed so water will go into tank-5 from tank-1 but not go to tank-2. Therefore tank-5 will be filled first.

Solution:

No wheels which imply car is not moving :-)

Solution:

As shown in the picture below.
Cut 1 : Cut the cake across the diameter.
Cut 2 : Cut horizontally and you will get 4 equal pieces of cake
Cut 3 : Cut horizontally from other side and you will get 8 equal pieces of cake

Solution:

John Walters was drowned in the quicksand.

Solution:

All Digits [0-9] follow the following pattern: There is one occurrence of all digits in every 10 numbers Example. Digit-9 occurred one time between 10 and 19 in 9, between 20 and 29 in 29
However, for tens(91,92,93...99) and hundreds (900,901.... 999), the occurrence is much more. Since we have included 1000, Therefor 1 is the most occurred digit.
Note: Despite three '0s' in 1000, 0 is not most occurred digit as they don't have tens and hundreds like other digits.

Solution:

100

Series of number that do not contain albhabet 'T'