Would C bond with H or D?
C-H would be the weakest bond, then C-D, then C-T would be the strongest.

This is due to the zero point energy of the bond and the fact the zero point energy is proportional to:

$$\sqrt{\frac{m_C + m_H}{m_C m_H}}$$

Zero point energy is the minimum energy the quantum harmonic oscillator can have.

Because the greatest mass isotope has the smallest zero point energy, the energy of the bond is greatest.