According to the different buying and selling directions of spreads, the intertemporal arbitrage of treasury bonds futures can be divided into two types: buying arbitrage and selling arbitrage of treasury bonds futures. Item a is correct. The cross-variety arbitrage trading strategy of treasury bonds futures is mainly based on the different sensitivity of bonds with different maturities to changes in market interest rates, and item B is correct. Generally speaking, bonds with long maturities are more sensitive to interest rate changes than bonds with short maturities. Item c is correct. When the investor's expected yield curve is steeper, he can buy short-term treasury bonds futures and sell long-term treasury bonds futures to realize the arbitrage of "buying yield curve", and item D is correct. So the answer to this question is ABCD.