Fill in the blanks using the correct word given in bracket:(i)         All circles are______(congruent, similar)
(ii)        All squares are_____. (similar, congruent)
(iii)       All______triangles are similar, (isosceles, equilateral)
(iv)       Two polygons of the same number of sides are similar, if
(a) their- corresponding angles are___and
(b) their- corresponding sides are__(equal, proportional)

Explanation

Let's solve the question step by step.

### Step 1: Analyze the first statement
The first statement is "All circles are ______ (congruent, similar)."
- **Explanation**: Congruent shapes are identical in size and shape, while similar shapes have the same shape but can be different in size. All circles have the same shape (they are round) but can have different radii. Therefore, all circles are similar.

**Answer**: All circles are **similar**.

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