On the last gray hour before sunset, I slipped into Mr. Dunn's boathouse to return the borrowed net. The power on the pier had been out all afternoon, yet a thin, steady hum came from the rafters, like a mosquito behind glass. Near the door, a silver key swung from a nail shaped like an anchor. The salt-stiff raincoat that usually hung beside it was gone. Scout, my neighbor's dog, padded after me but stopped at the threshold, ears flat, a small whine trapped in his throat. A cold draft carried a faint, smoky smell, though the iron stove sat dark and clean. When I set the net on the workbench, a loose floorboard near the trapdoor sighed under my weight. Beside it coiled a rope with a frayed end, as if it had been cut in a hurry. A tide chart lay open with Friday's square smudged. The lantern's glass was cloudy with soot. I backed away, heart tapping. Whatever Mr. Dunn had locked below, it hadn't stayed put.

Which plot technique primarily advances the story by hinting that a later discovery will occur in the boathouse?

We pushed our kayaks into the Guadalupe just as the light went thin and the wind shifted across the Hill Country. The air smelled of wet cedar and dust. Upstream, the sky stacked itself into dark shelves. Water that had been glass all morning began to shiver, tugging at our paddles. A low roll of thunder stitched the hills together. Our two-way radio crackled with a ranger's warning to watch for fast rises. We clipped our helmets and scanned the banks for the painted mark where the river bent toward a limestone ledge. Gravel bars we had walked across at noon were vanishing under a skin of foam. "Keep left!" I called, digging harder, my arms burning. A branch spun past like a thrown spear. We needed to reach the takeout before the storm reached us, but every stroke seemed smaller than the current. The first cold drops hit, fat and spaced far apart, as if counting down. The river wasn't raging yet, but it was gathering itself.

Which plot element is being developed as the danger increases on the river but the main conflict has not yet peaked?

The final round had been a mess. One loose wire kept our robot from sensing the blue ring, and the timer was already bleeding away the last seconds. I crouched beside the mat, tools shaking. "Ten," someone whispered. I had time for one choice—reset or risk. I popped the battery clip, twisted the sensor a hair to the left, and jammed the clip back home. The robot's status light flickered, then steadied. "Go," I said, breathless. Our bot shot forward, veered, and for a terrible heartbeat I thought it would miss again. The camera caught the edge of the ring. The arm dropped. Metal scraped. The ring lifted, slid, and settled onto the goal peg as the horn blared. The gym fell silent and then exploded around us, but I only looked at the field, waiting to see if the ring would wobble off. It didn't. All the hours in the lab collapsed into that tight, shining second.

Which plot element does this moment most clearly represent?

Fog draped the Strand in Galveston so thick the streetlamps were halos. From the seawall came a distant horn and the hush of waves folding over themselves. I was supposed to meet Aunt Lina at the old hotel to return the lost cameo, but the lobby lights had blinked and gone dark. The generator coughed once, then quit. My footsteps sounded too loud on the marble stairs. One flight. Pause. Listen. Another. The air cooled as I climbed, smelling of salt and polish. At the second floor landing, a door eased shut somewhere down the hall. Not slammed. Eased. I gripped the cameo in my pocket. My phone screen glowed and then dimmed, the battery icon a sliver. I didn't want to call out and announce myself. I didn't want to turn back either. A thin draft combed the hair at my neck. I held my breath, counting to three. The knob of Aunt Lina's room was cold. It turned.

How does the author's use of short sentences and sensory details advance the plot in this excerpt?