Select the most appropriate option to fill in the blank.

The reality of the effects of rising aviation industry emissions on climate change has been known for decades, yet the industry and its emissions has continued to grow without _________.

constraint

The most appropriate option to fill in the blank is:constraint

• Easiness and comfort imply a lack of difficulty or opposition, which wouldn't be the case if the industry is growing unchecked.
• Neglect suggests a lack of attention, but the sentence implies they are aware of the issue.
• Constraint signifies a restriction or limitation that is being bypassed by the continued growth. This aligns with the idea that the industry is not being held accountable for its emissions.

Therefore, "constraint" best captures the idea that the aviation industry is growing despite the known negative effects on climate change.