Please select the most similar patent number from A, B, C and D. Which number is?
A fixed vehicle safety inspection system comprises a ray source (10), a vehicle tractor and a detector (11). The vehicle tractor comprises a front fork arm (1), a rear fork arm (3), a front fork arm shaft (2), a rear fork arm shaft (4), a traction mechanism (5), a control unit, a drive unit and a traction passage (7). The front fork arm (1) and the rear fork arm (3) are connected to the front fork arm shaft (2) and the rear fork arm shaft (4) respectively, and can horizontally rotate around the front fork arm shaft (2) and the rear fork arm shaft (4) respectively under the control of the control unit. The front fork arm shaft (2) and the rear fork arm shaft (4) are arranged with one behind the other and are connected with the traction mechanism (5); the axial directions of the front fork arm shaft (2) and the rear fork arm shaft (4) are both perpendicular to the surface of the traction mechanism (5).
A: Disclosed are a vehicle traction device and a radiation imaging checking system. The vehicle traction device comprises a frame body (1) and a vehicle wheel fixing structure, wherein the vehicle wheel fixing structure is connected to the frame body (1), and is used for fixing wheels of a detected vehicle; and in a scanning plane perpendicular to an emitting direction of a ray, the projection of the frame body (1) is located on an outer side of the projection of a vehicle body of the detected vehicle. The projection of the frame body (1) of the vehicle traction device is located on the outer side of the projection of the vehicle body of the detected vehicle, and therefore, compared with the prior art, the frame body (1) does not obstruct the ray for detecting the detected vehicle, thereby improving the imaging quality.
B: A hand-driven bicycle including a handlebar (1), a vertical tube (2), a flywheel(8) mounted on the front wheel and a steel wire (16). The first end of the vertical tube is fixedly connected with the handlebar. The second end of the vertical tube is rotatably connected with a fork arm (6). A rocker arm (14) is extended from the second end of the vertical tube towards the front wheel&#39;s direction. The vertical tube is fixed together with the rocker arm, which form the power lever. The first end of the steel wire is fastened at the end location (7) of the fork arm. The second end of the steel wire is fixed on the flywheel of the front wheel around a pulley(15) on the free end of the rocker arm. While the handlebar is moved back and forth, the free end of the rocker arm is also moved back and forth, which drives the flywheel rotate through the steel wire so as to drive the front wheel run. The hand-driven bicycle enhances its speed and brings the cyclists&#39; body movement.
C: Disclosed is a lead-out type independent suspension with multiple supporting points, comprising an upper fork arm (1), a lower fork arm (2), elastic members (3), a damper (4) and a fork arm positioning shaft (5), wherein the upper fork arm (1) and the lower fork arm (2) are A-shaped structural components, the front ends of the upper fork arm (1) and the lower fork arms (2) are respectively connected to an upper hanging point and a lower hanging point of a vehicle wheel (C) via master pins (B), the rear ends of the upper fork arm (1) and/or the lower fork arms (2) are connected to a vehicle frame in different damping manners, and the damper (4) is mounted on an upper part of the front end of the upper fork arm (1). The upper and lower fork arms of the independent suspension construct reasonable vehicle supporting shaft points and transferring components, by using a lever, a torsion bar and the principle of moment of force, enables the shaft hanging points of the upper and lower fork arms to absorb a borne elastic force by means of a retracing force and the arm of a force or by changing directions, so as to be configured that multiple points support multiple elastic members so as to realize multipoint decomposition of the force sustained by the vehicle wheel to increase an average driving speed. The increase in the number of elastic members and the reasonable arrangement thereof can lower the height of the vehicle, and further optimize the space usage, thereby improving the stability and the running smoothness of the vehicle.
D: An improved bicycle frame structure, comprising a frame (1), a rear fork foot (2), a front fork foot (3) and a bottom bracket (4), the rear fork foot (2) and the front fork foot (3) being respectively fixed to rear and front ends of the frame (1), and the bottom bracket (4) being located at a lower end of the middle of the frame (1). Inner bearing positions are provided in both the rear fork foot and the front fork foot, so that a rear wheel carrier bearing (6) and a front wheel bearing (5) are respectively and correspondingly fitted in the respective inner bearing positions. The front fork foot and the front wheel bearing are fixed and connected by a front wheel hub fixing pin (11) in a penetrating manner, a front wheel hub (8) is sheathed on the front wheel hub fixing pin, and there is no need to provide corresponding bearings in the front wheel hub. The rear fork foot and the rear wheel carrier bearing are fixed and connected by a rear wheel hub fixing pin (12) in a penetrating manner, a rear wheel hub (9) is sheathed on the rear wheel hub fixing pin, and there is no need to provide corresponding bearings in the rear wheel hub. Outer bearing positions are provided on both ends of a horizontal straight tube of the bottom bracket, a crankshaft bearing (7) is sheathed on each of the outer bearing positions, a crankshaft (10) is sheathed on the outside of the crankshaft bearing, and a main shaft of the crankshaft is arranged to be penetrating the horizontal straight tube of the bottom bracket and fixedly connect two crankshafts. The frame structure simplifies the structure of a hub, reduces the difficulty of manufacturing the hub, and improves the bending resistance and torsion resistance of a crankshaft.
Answer: A