Read the following paragraph carefully and cross out the sentence which breaks unity.①Each of the Russian manned space exploration projects had specific major goals. ②For example, the Vostok project was designed to test whether or not human beings could survive and function in outer space. ③For another example, the Voshkhod project was intended to find out whether people could work in the weightless environment of space. ④One Voshkhod cosmonaut experimented with weightlessness by taking a "spacewalk." ⑤That is, he floated in a spacesuit outside his Voshkhod spacecraft, connected to it by a tether. ⑥The cosmonaut to do this was Alexei Leonov. ⑦Several weeks later, Leonov's spacewalk was followed by that of U.S. astronaut Ed White. ⑧Finally, the Soyuz project, with three cosmonauts, had goals of testing spacecraft and spaceflight skills so that people could fly long missions in Earth orbit.