Select the most appropriate option to fill in the blank.

Now after the COVID-19 situation has _________, Bangladesh has started air travel services for other countries including  India.

improved

The most appropriate option to fill in the blank is improved.

The word "improved" means to make something better. In this context, it means that the COVID-19 situation in Bangladesh has gotten better to the point where air travel services can be resumed.

The other options are not appropriate because they do not mean the same thing as improved. The word "progressed" means to make gradual advancement. The word "advanced" means to move forward or make progress. The word "enriched" means to make something more valuable or interesting.