Amplification results when an enzyme associated with a signal receptor is activated and, in turn, catalyzes the activation of many molecules of a second enzyme, each of which activates many molecules of a third enzyme, and so on, in a so-called _____________________.

The<br/>major role of the complement system is to work in conjunction with: A: antibodies to lyse cells via the C8 and C9 components B: the<br/>major histocompatibility complex for cell recognition C: antibodies to opsonize cells D: the<br/>T-cell receptor for production of lymphokines E: antibodies to lyse cells via the perforin molecules

Which of the following about cell cycle is NOT true？（ ） A: We can get the synchronization of the cells by blocking DNA synthesis by TdR. B: Cytokinesis of animal cells is mediated by a contractile ring of actin and myosin II filaments. C: Meiosis II is similar to meiosis I. D: According to the characteristics of cell division, cell groups can be divided into three types, such as Cycling cells, Terminally Differentiated cells and Quiescent cell.

Methotrexate kills some types of cancer cells by inhibiting _____________________, an enzyme that produces a compound required for DNA synthesis during cell division.

The cells belonging to the outermost layer of the retina are: A: Pigment epithelial cell B: Bipolar nerve cell C: Cone cell D: Ganglion cell