Answer:
3. Sn
Step-by-step explanation:
Locate the elements in the Periodic Table.
The ones with the most similar properties will be next to each other in the same Group.
Sn is just below Ge in Group 14, so Sn is most like Ge.
Ga, Zn, Cu, and Na are progressively further from Ge in the Periodic Table, so they have quite different properties.
Here are some of the properties of Ge and Sn.
Most common oxidation state = +4
Halide = MX₄
Oxide = MO₂
Type of oxide = amphoteric
Electronegativity = 2.0