(a) As we know that,

The opposite of the word Increase is Decrease

Hence,

According to the question,

The opposite of ‘Increase in weight’ would be ‘Decrease in weight’.

(b) As we know that,

The opposite of the direction North is South

Hence,

According to the question,

The opposite of ’30 km North’ would be ’30 km South’.

(c) As we know that,

The opposite of the word BC is AD

Hence,

According to the question,

The opposite of ‘326 BC’ would be ‘326 AD’

(d) As we know that,

The opposite of the word Loss is Profit

Hence,

According to the question,

The opposite of ‘Loss of 700’ would be ‘Profit of Rs 700’.

(e) As we know that,

The opposite of the word above is below.

Hence,

According to the question,

The opposite of ‘100 m above sea level’ would be ‘100 m below sea level’.