( ( ( How many ) ( ( ( asteroids ( AKA ( Near-Earth Asteroids ) ) ) ( -LRB- ( NEA -RRB- ) ) ) ( ( ( are ( in space ) ) and ) ( ( may still ) ( collide ( with Earth ) ) ) ) ) ) . )
(ROOT (SBAR (WHADJP (WRB How) (JJ many)) (S (NP (NP (NNP asteroids) (NNP AKA) (NNP Near-Earth) (NNP Asteroids)) (PRN (-LRB- -LRB-) (NP (NNP NEA)) (-RRB- -RRB-))) (VP (VP (VBP are) (PP (IN in) (NP (NN space)))) (CC and) (VP (MD may) (ADVP (RB still)) (VP (VB collide) (PP (IN with) (NP (NNP Earth))))))) (. .)))
How many asteroids AKA Near-Earth Asteroids (NEA) are in space and may still collide with Earth.
(ROOT (S (PP (IN In) (NP (DT the) (NN past))) (, ,) (NP (NP (NNS asteroids)) (VP (VBG colliding) (PP (IN with) (NP (NN planet) (NN earth))))) (VP (VBZ has) (VP (VBN caused) (NP (JJ many) (NNS organisms)) (S (VP (TO to) (VP (VB die) (PRT (RP off))))))) (. .)))