help with parallelograms

i'm not exactly sure how to explain these, but i believe number 3 is the answer.

here is a site that describes the properties of a parallelogram:

https://www.mathplanet.com/education/geometry/quadrilaterals/properties-of-parallelograms

if you have any further questions on why 1, 2, and 4 are not properties of a parallelogram, feel free to ask! 

hope this helped!