1. Answer;
- Triangle
Explanation;
The cross section formed by a plane that contains a vertical line of symmetry for a tetrahedron is a Triangle.
A tetrahedron also a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners.
2. Answers
- Triangle
Explanation;
The cross section formed by a plane that intersects three faces of a cube is a Triangle. A cross section is the shape we get when cutting straight through an object. The shape of the cross-section of a solid depends upon the orientation of the cutting plane to the solid.
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The complete question is shown below. As you can see, we know that:

Shapes are congruent if you can turn one into the other by moving, rotating or flipping. If any two triangles have matching side lengths, they're not necessarily congruent. The same happens if they have two matching side lengths, but If triangles have three matching side lengths, then they must be congruent. This is is known as the Side-Side-Side Postulate (SSS). Since in this problem corresponding sides measures the same, therefore we can say that the postulate that applies is:
B. Congruent - SSS
Answer:
A) only figure 1 and figure 2
Step-by-step explanation: