Complete the sentence using appropriate option.
The quality of products __________ over time.

Correct option is C

The correct option to fill in the blank is (c) have been degrading.
The quality of products is a singular subject, but the focus is on the continuous process over time. The present perfect continuous tense ( have been degrading) is used to describe an action that started in the past and is still ongoing.
Grammatical rule used: Present Perfect Continuous Tense: This tense is used for actions that began in the past and continue to the present.
Explanation of the grammatical rule in Hindi: जब कोई क्रिया (action) अतीत में शुरू हुई हो और अभी तक जारी हो, तो Present Perfect Continuous Tense का प्रयोग किया जाता है। यहाँ उत्पादों की गुणवत्ता में गिरावट समय के साथ जारी है, इसलिए have been degrading सही विकल्प है।
Meanings of other options:
· have degrading: Incorrect tense structure; lacks auxiliary verb for continuous tense.
· were degraded: Simple past passive tense; suggests the action is completed, but the sentence implies it’s ongoing.
· are degrading: Present continuous tense; suggests a current action but doesn’t cover the aspect of time as effectively as the perfect continuous tense.