निम्नलिखित वैज्ञानिकों में से किसने एक्स-किरणों (X-rays) की खोज की थी?

Taking a glass of water and freezing it by placing it inside a freezer is an example of which type of change and process?

Which of the following statements is/are true about air pressure? (A) Air around us exerts very less pressure on us. (B) Air contracts on heating and expands on cooling. (C) Warm air rises up and cooler air tends to sink towards the earth's surface. (D) As warm air rises, air pressure at that place is decreased.