Astronomers have recently discovered an asteroid, 2002 NT7,

Yes....it said scientist discovered ....so could be preferred i think..

Option C

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we can eliminate B and E, c seems more convincing

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Can anyone tell me why not answer B?
B. and could, according to current calculations, possibly strike Earth on

Can someone explain why option B is wrong?

123s4df snehakr1603

In part, B is wrong because "could possibly" is redundant. We can cut "might possibly" in E for the same reason. If we say that something COULD or MAY or MIGHT happen, we're already saying it's possible. Of course, people talk this way all the time, but the GMAT is more precise than that.

In particular, B is saying "An event could occur on February 1, 2019. What event? An asteroid possibly striking Earth." But we can't say that at a certain time, the asteroid will "possibly strike." Either it strikes or it doesn't. Rather, we'd say something like "It's possible that the asteroid will strike on Feb 1."

It's also useful that C and D start with "that." Technically, we can use "has" and "could" as parallel verbs. However, they're not terribly well-related: HAS is used for a passive clause describing the asteroid's size, while COULD is used for an active clause describing what the asteroid might do. Adding THAT turns these into two parallel modifiers, each of which provides a different detail about the asteroid.