Final answer:
An equilateral parallelogram with all sides equal is known as a square, which fits the description provided. Thus, the correct answer is option c) Square.
Step-by-step explanation:
You have described an equilateral parallelogram, which is a four-sided figure with all sides of equal length and opposite sides parallel to each other. In geometric terms, the only parallelogram that has four sides of equal length and is also equilateral is a square. A square fits your description perfectly as it has all sides of equal length and each angle is a right angle, making all four angles total 360 degrees.
If we examine the options provided: a rectangle has four right angles but typically sides of differing lengths; a rhombus has all sides of equal length but not necessarily four right angles; a square has both features; and a trapezoid does not have all sides of equal length nor is it always symmetrical.
Therefore, the correct answer to your description of an equilateral parallelogram is option c) Square.