Correct Answer: continuous

Solution : The correct choice is the fourth option .

Gradual means taking place or progressing slowly.

Continuous refers to something that occurs without interruption or breaks, which aligns with the idea of something happening steadily or progressively, and hence is synonymous with "gradual".

The meanings of the other options are as follows:

• Abrupt means something unexpected.
• Hasty means hurried.
• Uneven is something that is not levelled.