Improve the underlined verb phrase in the sentence: "The custom has took root in the society."

Introduction / Context:
This sentence improvement question focuses on correct verb forms in the present perfect tense. The sentence describes a custom that has become firmly established in society. You must select the correct form of the verb take to follow has in a standard verb phrase.

Given Data / Assumptions:
The original sentence is:

• The custom has took root in the society.

The options for the underlined part are:

• taken root
• take root
• takes root
• No improvement

Concept / Approach:
In English, the present perfect tense is formed with has or have followed by the past participle of the main verb. The base form is take, the past tense is took, and the past participle is taken. Therefore, after has we must use taken, not took. The idiom take root or taken root describes something that becomes established or begins to be accepted.

Step-by-Step Solution:
Step 1: Identify the tense sign. The auxiliary has shows that the sentence is in the present perfect tense. Step 2: Recall the forms of the verb: take, took, taken. Step 3: In present perfect, has must be followed by the past participle taken. Step 4: Evaluate taken root. This matches the pattern has taken root, which is the correct idiomatic expression. Step 5: Evaluate take root. This is the base form and would be correct with will or can, but not with has. Step 6: Evaluate takes root. This is present simple and does not fit after has. Step 7: Evaluate No improvement. Keeping has took root would be grammatically wrong. Step 8: Therefore, taken root is the correct improvement.

Verification / Alternative check:
Read the improved sentence: The custom has taken root in the society. This is a common and correct phrase indicating that the custom has become well established. You might also say The tradition has taken root over the years. In all such cases, has or have is followed by the past participle taken, not the past form took.

Why Other Options Are Wrong:
Take root is wrong here because it would require a different auxiliary, such as will or can, for example The custom will take root. Takes root is wrong because it forms a simple present construction, as in The custom takes root slowly, and not a present perfect structure. No improvement is wrong because has took is not a standard combination in English grammar.

Common Pitfalls:
A frequent mistake is confusing the past tense took with the past participle taken. Many learners apply the past tense form after has or have, which is incorrect. It is important to memorise irregular verb tables and practice them in sentences. For example, write out sequences like take, took, taken; speak, spoke, spoken; write, wrote, written. This habit strengthens your control over perfect tenses.

Final Answer:
The correct improvement is taken root.