Question 1
Light and variable winds

which caused difficulties for mariners in the days of sailing ships

occur under the
◦ subpolar low and equatorial low.
◦ subpolar low and subtropical high.
◦ equatorial low and subtropical high.
◦ equatorial low and subpolar low.
Question 2
Mountain-valley breezes are caused by
◦ warmer air descending mountain slopes during the day.
◦ valley air ascending the mountain slopes at night.
◦ warm air rising upslope during the day and cooler air descending the slopes at night.
◦ gravity-drainage.