Equal replication and $\lambda=3$ for every pair, but unequal blocks

Layout of a block design with 5 blocks and 4 treatments A, B, C, D is: Block 1: A, B, C; Block 2: A, B, D; Block 3: A, C, D; Block 4: B, C, D; Block 5: A, B, C, D. Which one of the following statements is true?