Which of the following is considered to be an acid a) hci b)koh c)naoh d)ca(oh)2

The correct answer is option A, that is, HCl.  

An acid refers to an ion or molecule possessing the tendency of donating a hydrogen ion or a proton, or alternatively, exhibiting a tendency of producing a covalent bond with a pair of electrons. The aqueous Arrhenius acids exhibit characteristic features that offer a practical illustration of an acid.  

The acids can turn blue litmus paper red, can form aqueous solutions with a sour taste, and reacts with bases and some kind of metals to produce salts. One of the general aqueous acids is HCl (hydrochloric acid) that is found in the stomach and stimulates digestive enzymes.  

under a microscope, cancer cells may look very different from normal cells. they often have different sizes and some may be larger than normal while others are smaller. cancer cells are often abnormally shaped and the control centre of the cell (the nucleus) may have an abnormal appearance.

i think? ?

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.