1. .......... express CD3 and CD4 molecules.

A) Ts and Tc cells
B) Th1 and Tc cells
C) Th1 and Th2 cells
D) All T cells

... Answer is B) - Th1 and Tc cells

CD3: The CD3 complex is comprised of several molecules associated with the T-cell antigen receptor. It is composed of six polypeptides and is found on all T cells. It provides support for the TCR and is involved in trans-membrane signaling when the TCR is filled.

CD4: CD4 is a 55-kDa molecule belongs to the Ig supergene family with four immuno- globulin-like domains. A cell-surface molecule, CD4 is found in association with the TCR on approximately two-thirds of mature T cells (the T-cell subset known as helper T (Th) cells). CD4 molecules recognize the lateral, nonpeptide-binding portion of MHC class II molecules. The TCRs of CD4+ T cells are "restricted" to the recognition of MHC class-II peptide complexes.