This is because of the differences in the nature of the surfaces of both the planets. The surface of Mercury is made of volcanic rocks and craters, so very little light is reflected from its surface. The planet reflects only 6 per cent of the incident light. In contrast, Venus has a dense atmosphere consisting of carbon dioxide. The surface of the whole planet is covered by carbon dioxide clouds and thus Venus reflects almost about 76 per cent of the Sun's light making it look brighter and shinier, almost like a diamond.
Most launch vehicles are multi-stage rockets with two or three separate rocket stages.
The stages are joined together end to end. The first stage gives the ones above it a ride into space. After it has run out of fuel, it falls away. The second stage takes over, using its own engines. The tallest multi-stage rocket ever built was the American Saturn V rocket made up of three stages.