Final answer:
The received bits 10101001 satisfy even parity with an even number of 1s, indicating the received data is likely correct with 1010100 as the usable part.
Step-by-step explanation:
When dealing with digital data transmission, parity bits are used for error detection. Even parity means that the total number of 1s in the sequence, including the parity bit, should be even. The sequence 10101001 has an even number of 1s (four 1s), and thus the even parity condition is satisfied without adding an additional 1. Therefore, the received data is correct as it stands, and the usable part is 1010100, with the last 1 likely being the parity bit.