Correct Answer: st or mo

Solution : Given:
1. chips are good ⇒ lo pur tan
2. soul are mate ⇒ tan fu gil
3. chips contain metal ⇒ pur st mo

By comparing all the three coded sentences –
In sentences 1 and 3, chips and pur are common.
In sentences 1 and 2, are and tan are common.

The remaining words and codes in sentence 1 are good and lo . So, lo will work as a code for good .

Finally, chips ⇒ pur; are ⇒ tan; good ⇒ lo ; contain/metal ⇒ st/mo; soul/mate ⇒ fu/gil

Contain is coded as st or mo . Hence, the fourth option is correct.