1, 2 and 3 are correct.
The largest reservoir of Earth’s oxygen is within the silicate and oxide minerals of the crust and mantle (99.5%). Only a small portion has been released as free oxygen to the biosphere (0.01%) and atmosphere (0.36%). The main source of atmospheric free oxygen is photosynthesis.
The processes that lead to loss of oxygen are:
• Aerobic respiration (largest – more than 75%)
• Microbial oxidation
• Combustion of fossil fuel (anthropogenic – around 6-7% loss only)
• Photochemical oxidation
• Fixation of N2 by lightning
• Fixation of N2 by industry (anthropogenic)
• Oxidation of volcanic gases
• Chemical weathering
• Surface reaction of O3

Only statement 1 is correct.
Alpha is the diversity within an ecosystem which is generally described as the number of species.
Beta diversity involves the comparison of different ecosystems in environmental gradients, for example, in a mountainous area within a coastal area. Beta diversity shows us the size of the change of species from one ecosystem to another.
Gamma diversity refers to the total diversity of a region, i.e. the geographic diversity. It is the sum of the alpha diversity of various ecosystems.

Statement 2 is incorrect.
Savanna or Sudan climate is a transitional type of climate found between the equatorial forests & trade wind hot deserts.
• It is confined within the tropics (Tropic of Cancer & Tropic of Capricorn) & is best developed in Sudan, where dry & wet climate are most distinct, hence named Sudan climate.
• It covers much of Africa (Keya, Nigeria, Gambia) as well as large areas of Australia, South America (Brazilian highlands), and India.
• Sudan climate is characterized by an alternate & distinct hot, rainy season (from May to Sep) & cool, dry season (Oct – April) in Northern Hemisphere& vice versa in Southern Hemisphere.

Statement 2 is correct.
A few organisms can tolerate and thrive in a wide range of temperatures (they are called eurythermal), but, a vast majority of them are restricted to a narrow range of temperatures (such organisms are called stenothermal).
Many freshwater animals cannot live for long in sea water and vice versa because of the osmotic problems, they would face.

Vermicomposting is a type of composting in which certain species of earthworms are used to enhance the process of organic waste conversion and produce a better end-product. It is a mesophilic process utilizing microorganisms and earthworms. Earthworms feeds the organic waste materials and passes it through their digestive system and gives out in a granular form (cocoons) which is known as vermicompost.
A wide range of organic residues, such as straw, husk, leaves, stalks, weeds etc. can be converted into vermicompost. Other potential feedstock for vermicomposting production are livestock wastes, poultry litter, dairy wastes, food processing wastes, organic fraction of MSW, bagasse, digestate from biogas plants etc.