20) the following are characteristics of cancer cells except for a) cancer cells undergo apoptosis b) cancer cells form tumors c) cancer cells lack differentiation d) cancer cells have abnormal nuclei e) cancer cells undergo metastasis and angiogenesis

(a). Cancer cells undergo apoptosis.

Explanation:

Cancer cells are cells that undergo uncontrolled cell division and form tumors.  Other characteristics cancer cells include abnormal cell nuclei (unstable genetic material due to mutations), lack of cell differentiation, angiogenesis,. and metastasis (spread of cancer cells to other body parts).

Cancer cells do not go for normal cellular death as these cells bypass the apoptosis (programmed cell death). Hence, cancer cells are considered as immortal cells.  

Thus, the correct answer is option (a).

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.