__ Substances arranged in the sequence: oxide - base - salt , are in a row Answer 1. H_(2)O- LiOH- KHCO_(3) 2. P_(2)05- ZnSO_(4) Ba(OH)_(2) 3. OF_(2)- NaOH- Pbl_(2) 4. CaO- H_(2)CO_(3) -NaOH

The correct answer is option 4: $CaO-$ $H_{2}CO_{3}$ $-NaOH$.<br /><br />In this sequence, the substances are arranged in the order of oxide, acid, and base. <br /><br />1. $CaO$ is calcium oxide, which is an oxide.<br />2. $H_{2}CO_{3}$ is carbonic acid, which is an acid.<br />3. $NaOH$ is sodium hydroxide, which is a base.<br /><br />Therefore, the correct answer is option 4.