The structure that provides buoyancy to aquatic plants is: MCQ with Answer and Explanation

Explanation:
Mammalia is the only class of animals that possess mammary glands, which produce milk to nourish their young ones. Other defining features of mammals include the presence of hair on the skin, external pinnae (ear flaps), a four-chambered heart, and being warm-blooded (homeothermic). Examples include humans, whales, and bats.

Explanation:
A mature embryo sac (female gametophyte) in angiosperms is 7-celled but 8-nucleate: 3 antipodal cells (3 nuclei), 2 synergids (2 nuclei), 1 egg cell (1 nucleus), and 1 central cell with 2 polar nuclei. Thus total 8 haploid nuclei. The central cell is homodiploid (2 polar nuclei). Double fertilization involves these nuclei. This is typical of Polygonum type of development.

Explanation:
Body Mass Index (BMI) is a simple index used to classify underweight, overweight, and obesity. It is calculated as a person's weight in kilograms divided by the square of their height in meters (kg/m2). While it is a useful population-level screening tool, it does not directly measure body fat and may not be accurate for athletes or the elderly.