आंसू गैस (tear gas) में सक्रिय घटक के रूप में आमतौर पर निम्नलिखित में से किस गैस का उपयोग किया जाता है?

Patients are instructed to swallow a suspension of which compound as a radiopaque contrast agent before undergoing X-ray examination of the gastrointestinal tract?

To combat anemia and iodine deficiency disorders, the Government of India promotes 'double fortified salt'. Which two essential minerals are added to this salt?