Correct Answer: 7

Solution : Given:
1. high and low ⇒ 567
2. b uildings are high ⇒ 629
3. hot and sour ⇒ 531

By comparing all the three coded sentences, we find that –
In sentences 1 and 2, high and 6 are common.
In sentences 1 and 3, and and 5 are common.
The remaining words and codes in sentence 1 are low and 7, in sentence 2 are buildings , are and 2 , 9 , and in sentence 3 are hot , sour and 3 , 1 .

So, low will be coded as 7 . Hence, the third option is correct.