The correct answer is option 'A' (yellow).

Explanation:

When choosing the correct adjective to complete the sentence, we need to consider the context and meaning of the sentence. In this case, the sentence is referring to the flowers in the garden and their current state of blooming.

To describe the flowers, we need an adjective that indicates their color. The adjective should match with the plural form of the noun 'flowers' and should also convey the idea that the flowers are currently in the process of blooming.

Let's analyze the given options and see which one fits the context:

a) yellow: This adjective describes the color of the flowers. It matches with the plural noun 'flowers' and indicates a specific color, but it doesn't convey any information about the state of blooming. However, it is still the most appropriate choice as it describes the color of the flowers in the garden.

b) yellowsc: This is not a valid adjective. It appears to be a misspelling.

c) yellower: This is a comparative form of the adjective 'yellow'. However, it doesn't fit the sentence as it implies a comparison between two or more things. The sentence doesn't provide any basis for comparison, so this option is not suitable.

d) yellowest: This is a superlative form of the adjective 'yellow'. Similar to the previous option, it implies a comparison between multiple things. Since the sentence doesn't provide any basis for comparison, this option is also not appropriate.

Therefore, the correct adjective to complete the sentence is 'yellow' (option A), as it accurately describes the color of the flowers in the garden.