The correct answer is (a). Mangroves are salt tolerant. They are able to grow in saline water because they have special adaptations that allow them to exclude salt from their tissues. These adaptations include salt glands, which excrete excess salt, and a waxy coating on their leaves, which helps to prevent water loss.
(b) is incorrect because mangroves are not tolerant of sugar. In fact, high levels of sugar can be toxic to mangroves.
(c) is incorrect because mangroves are not tolerant of cement. Cement is a type of concrete that is made from sand, gravel, and cement. It is very hard and can damage the roots of mangroves.
(d) is incorrect because mangroves are not tolerant of nitrogen. Nitrogen is an essential nutrient for plants, but too much nitrogen can be harmful. Mangroves are particularly sensitive to nitrogen pollution from fertilizers and sewage.