Color the biggest red, tallest green, longest blue, and thinnest yellow.

Let’s go step by step to solve each part of the task.

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Part 1: Color the biggest umbrella red.

We have three umbrellas:
- Left: medium size
- Middle: largest (biggest)
- Right: smallest

→ The middle umbrella is the biggest → color it red.

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Part 2: Color the tallest tree green.

We have four trees:
- Far left: short
- Second from left: tall
- Third from left: tallest (has the highest top and longest trunk)
- Far right: medium height

→ The third tree from the left is the tallest → color it green.

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Part 3: Color the longest ribbon blue.

We have two ribbons:
- Top ribbon: shorter, wavy
- Bottom ribbon: longer, also wavy — stretches farther left to right

→ The bottom ribbon is the longest → color it blue.

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Part 4: Color the thinnest bottle yellow.

We have four bottles:
- First (left): wide base, thick
- Second: round body, fairly thick
- Third: narrow neck and thin body — this is the skinniest
- Fourth: wider than third, not as thin

→ The third bottle from the left is the thinnest → color it yellow.

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Final Answer:
Color the middle umbrella red, the third tree from the left green, the bottom ribbon blue, and the third bottle from the left yellow.