Based on the context, what is the best definition of the word illusion?

Ano ang ibig sabihin ng hugot lines

Alert inattentive or drowsy drivers when they veer off the road ?

On what political idea did president truman base the marshall plan? as economic aid increased in europe, the friendship of nations with the united states would increase. as peace throughout the world increased, the threat of another world war would decrease. as prosperity in europe increased, the threat of communism spreading would decrease. as the power of capitalism increased in europe, stalin's power in the soviet union would decrease.