Identify the correct form of verb/phrase out of the given choices so as to complete following sentences.

You had better ________ your mother, she's been very anxious.

The correct answer is 'call'.

Key Points

• The given sentence uses a compound modal 'had better'.
• It is used to indicate advisability. And some times even carries a hint of urgency or even threat or warning.
• It is used to recommend future action on a particular occasion.
• 'Had better' takes the root form of a verb after it.
  • Example  - We had better buy travel insurance this time.
• Therefore, the correct verb form following 'had better' is 'call.'

Hence, the correct answer is Option 4.