1. Correct. The answer is true. T by the property method describes the properties of the elements and is


T={metals with atomic numbers #: <21<#<48 or 72<# <80 or 104<#<112}

Alternatively describing T by the roster method gives a roster or list of the elements:

T = {Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Rf, Db, Sg, Bh, Hs, Mt, Uuu, Uub}