The correct statements from the following are :
A. Ionic radii of trivalent cations of group 13 elements decreases down the group.
B. Electronegativity of group 13 elements decreases down the group.
C. Among the group 13 elements, Boron has highest first ionisation enthalpy.
D. The trichloride and triiodide of group 13 elements are covalent in nature.
Choose the correct answer from the options given below :

Analyzing statements about Group 13 elements (B, Al, Ga, In, Tl):
A. Ionic radii of M³⁺ cations: Down a group, more electron shells are added, so ionic radii increase, not decrease. FALSE
B. Electronegativity: Generally decreases down the group, though Ga shows an anomaly with higher electronegativity than Al. The statement is approximately true but has exceptions.
C. First ionization enthalpy: B (800.6 kJ/mol) is highest due to smallest size and highest nuclear charge density. Al (577.5), Ga (579), In (558), Tl (589). TRUE
D. Trichlorides and triodides: BCl₃, AlCl₃, GaCl₃, etc. are all covalent compounds (electron-deficient). BI₃, AlI₃, GaI₃, etc. are also covalent (I⁻ is large and polarizable). TRUE
The clearly correct statements are C and D.