**Given Information:**
- Focal length of the convex lens = 12 cm
- Magnification produced by the lens = -1

**Formula:**
The magnification produced by a lens is given by the formula:

magnification (m) = - (image distance/object distance)

Where:
- magnification (m) is negative when the image formed is inverted
- image distance is the distance between the lens and the image formed
- object distance is the distance between the lens and the object placed

**Solution:**
To find the correct position for the object, we need to use the formula for magnification and rearrange it to solve for the object distance.

Given:
magnification (m) = -1
focal length (f) = 12 cm

Using the formula, we have:
magnification (m) = - (image distance/object distance)
-1 = - (image distance/object distance)

Since the magnification is -1, we can conclude that the image formed is the same size as the object, but inverted.

To find the object distance, we rearrange the formula:
object distance = - (image distance/magnification)

Since the image distance is not given, we need to find it using the lens formula:

1/f = 1/v - 1/u

Where:
- f is the focal length
- v is the image distance
- u is the object distance

Since the magnification is -1, the image distance will be equal to the object distance.

Substituting the given values into the lens formula:
1/12 = 1/u - 1/u

Simplifying the equation:
1/12 = 0

This equation is not possible, which means the object distance cannot be determined.

Therefore, the given information is inconsistent, and we cannot determine the correct position for the object.

I do think the answer is -12 . isf it is B then the magnification would be -2