Answer:
The option that does not properly nest control structures is:
```
count = 0
if count < 10:
for i in range(3):
print(count)
count = count + 1
```
The `if` statement is not properly nested within the `for` loop. As it is currently written, the `if` statement will only be evaluated once, before the `for` loop executes. This means that if `count` is less than 10 initially, then the `for` loop will always execute three times, regardless of the value of `count`.
To properly nest the control structures, the `if` statement should be inside the `for` loop, like this:
```
count = 0
for i in range(3):
if count < 10:
print(count)
count = count + 1
else:
break
```
This way, the `if` statement is evaluated for each iteration of the `for` loop, and the loop will terminate if `count` becomes larger than 10.