Select the most appropriate option to fill in the blank.

The sergeant could not stand the weather because it was ________ cold.

bitterly

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

The sentence is about the sergeant's inability to stand the weather because it was bitterly cold. The word "bitterly" means extremely cold or unpleasant. It is the most appropriate word to use in this context, as it describes the severity of the cold weather.

The other options are not as appropriate:

• Carefully means in a careful and cautious manner. It is not accurate to use "carefully" in this context, as the sergeant is not being careful or cautious about the weather.
• Smoothly means in a way that is free from difficulty or roughness. It is not accurate to use "smoothly" in this context, as the weather is not smooth or easy to deal with.
• Cautiously means in a way that is careful and aware of possible dangers. It is not as appropriate as "bitterly", as it does not convey the same sense of severity or unpleasantness.