Answer:

Yes, it could be a square. The pattern is a shape that is not four-sided followed by a shape that is four-sided. Since the last shape in the pattern is not 4-sided, the next shape must have four sides, so a square could be the next shape.

Teacher Notes:

Students in grades 3–5 should investigate numerical and geometric patterns and express them mathematically in words or symbols. They should analyze structures of patterns and how they grow and change. In addition, they should organize this information systematically and use their analysis to develop generalizations about the mathematical relationships in the pattern.2

2 National Council of Teachers of Mathematics. (2000). Principles and standards for school mathematics (pp. 159–160). Reston, VA: Author.