KEAM 2015 Physics and Chemistry Paper

Hardest lanthanide element is lutetium (‌71 Lu). But among the given options gadolinium (Gd) is the hardest lanthanoid.
Hardness of few lanthanide elements on vicker's scale is given below.

Lanthanides	Hardness (M Pa)
57La	491
62Sm	412
64Gd	570
66Dy	540
70Yb	206