Final Answer:
Strider observed three signs indicating Gandalf's presence at Weathertop: a fire had been lit, a bundle of sticks tied with a cord, and the stone marked with G for Gandalf.
Step-by-step explanation:
Upon arriving at Weathertop, Strider noticed three distinct indications of Gandalf's recent presence. Firstly, a small fire pit showed signs of a fire having been recently kindled. Secondly, a bundle of sticks bound together with a cord lay nearby, suggesting that Gandalf had prepared this makeshift setup during his stay. Finally, a stone marked with the letter "G" served as a clear sign that Gandalf had indeed been there. These three clues collectively confirmed Gandalf's visit to Weathertop, providing Strider with evidence of his passage through the area.
The presence of the fire indicated recent activity, as the remnants of charred wood and ash suggested a fire had been recently extinguished. The bundle of sticks and cord, commonly used by Gandalf during his travels, further supported the notion of his recent stay. Lastly, the marked stone acted as a deliberate sign or message left by Gandalf, possibly to convey his passage or intended direction to others. Altogether, these signs corroborated Gandalf's visit to Weathertop, aiding Strider in understanding the sequence of events and movements in the area.