ANS:A - bubble the gas through liquid.

For contacting a highly soluble gas with a liquid, either bubbling the gas through the liquid or spraying the liquid on the gas stream would suffice. Explanation:

• Bubbling the gas through the liquid: This method involves passing the gas through the liquid in the form of bubbles. As the bubbles rise through the liquid, they create a large interfacial area between the gas and liquid phases, facilitating mass transfer and allowing the highly soluble gas to dissolve into the liquid.
• Spraying the liquid on the gas stream: Alternatively, the liquid can be sprayed onto the gas stream. This method involves atomizing the liquid into small droplets and dispersing them into the gas stream. The gas-liquid contact occurs as the droplets mix with the gas, providing a large interfacial area for mass transfer and allowing the highly soluble gas to dissolve into the liquid.