What is meant by the statement that “science is tentative”?

Isaw my future flash before me and it did not take me anytime to slow down. i need to replace the words "it did".

Read the passage. (1) the first skateboard was constructed of old roller-skate wheels attached to a piece of wood. (2) improvements were made to the skateboard in 1959. (3) the year that the first commercially made skateboard appeared. (4) soon after, skateboarding began to grow in popularity. (5) in 1963, skateboard manufacturers formed the first professional skateboarding team. (6) that same year, the first organized skateboard competition took place, in california. which is the most effective way to correct the fragment in sentence 3? attach the fragment to sentence 4. attach the fragment to sentence 2. insert the phrase in the united states to the end of the fragment. insert the verb had before the verb appeared.

Hurry 20 mins left! study the timeline of russian history, and read the passage from chapter 1 of animal farm. "is it not crystal clear, then, comrades, that all the evils of this life of ours spring from the tyranny of human beings? only get rid of man, and the produce of our labour would be our own. almost overnight we could become rich and free. what then must we do? why, work night and day, body and soul, for the overthrow of the human race! that is my message to you, comrades: rebellion! " which event most likely influenced the writing of this passage? the 1905 massacre of people who were protesting their poor living conditions the 1917 bolshevik revolution, which was inspired by the ideals of lenin the development of the union of soviet socialist republics by lenin in 1922 the collectivization of agriculture by the communist party in russia in 1928