State TWO reasons how bacteria can be useful to humans,
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Creating products, such as ethanol and enzymes.

Making drugs, such as antibiotics and vaccines.

Making biogas, such as methane.

Cleaning up oil spills and toxic wastes. Bacteria have long been used by humans to create food products such as cheese, yoghurt, pickles, soy sauce and vinegar. We are also able to use bacteria to break down our sewage and to clean up oil spills.

Explanation:

1. glaciers are melting

2. more water going into ocean (water's such as fresh waters, etc)

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.