Answer:
Unyielding
Explanation:
Relentless means oppressively constant; incessant.
Accelerated means of a vehicle or other physical object) begin to move more quickly.
Occasional means occurring, appearing, or done infrequently and irregularly.
Haphazard means lacking any obvious principle of organization.
Unyielding means (of a mass or structure) not giving way to pressure; hard or solid as well as (of a person or their behavior) unlikely to be swayed; resolute.
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