Final answer:
The character in the 1873 Thomas Hardy serial dangles from an 'enormous sea-bord cliff', making 'a) Cliff' the correct answer.
Step-by-step explanation:
In the 1873 Thomas Hardy serial, the character ends up dangling from an "enormous sea-bord cliff". The correct answer to the question is option a) Cliff.
The context provided in the passages vividly describes marine adventures and perilous situations involving the sea, such as rolling in the trough of the sea, waves crashing down on boats, and a character holding onto a piece of life-belt in the water. These excerpts from different stories all showcase the dramatic and dangerous aspects of the sea, similar to the peril faced by the character in Hardy's serial.
It can be inferred from the text that 'sea-bord' refers to a region bordering the sea, and the term 'cliff' fits the description of what someone could dangle from. Thus, the term 'cliff' is typically associated with a steep sea border, making it the most likely choice.