1. The problem asks to identify which substance is a transition element used in high intensity lamps based on given electronic configurations and properties. 2. Recall that transition elements are defined as elements whose atoms have an incomplete d subshell or can form cations with an incomplete d subshell. 3. Analyze each option: - a) Contains 10 completely filled orbitals: This suggests a full d subshell (d10), which corresponds to elements like Zn, Cd, Hg. These are transition metals but often not used in high intensity lamps. - b) Electron configuration ends with $ns^{n-4}, (n-1)d^{n+3}$: This is unusual and does not match typical transition metal configurations. - c) Penultimate main level contains 17 electrons: The penultimate shell is the $(n-1)$ shell. Having 17 electrons there is unusual and does not correspond to typical transition metals. - d) Lies in the sixth period and the first column in the d-block: The sixth period d-block first column corresponds to element 73 (Ta) or 57 (La) if counting f-block separately. The first column in the d-block of period 6 is element 73 (Ta, Tantalum), a transition metal used in high intensity lamps. 4. Therefore, option d) correctly identifies a transition element used in high intensity lamps. Final answer: d) lies in the sixth period and the first column in d-block.