( ( ( ( ( Completion ( of ( this stage ) ) ) , ) ( at ( eight weeks ) ) ) , ) ( ( ensures ( ( ( ( the ( body systems ) ) ( are developed ) ) and ) ( ( ( from then ) on ) ( , ( ( the embryo ) ( is ( called ( the fetus ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NN Completion)) (PP (IN of) (NP (DT this) (NN stage))) (, ,) (PP (IN at) (NP (CD eight) (NNS weeks))) (, ,)) (VP (VBZ ensures) (SBAR (S (S (NP (DT the) (NN body) (NNS systems)) (VP (VBP are) (VP (VBN developed)))) (CC and) (S (ADVP (PP (IN from) (ADVP (RB then))) (IN on)) (, ,) (NP (DT the) (NN embryo)) (VP (VBZ is) (VP (VBN called) (NP (DT the) (NN fetus)))))))) (. .)))
Completion of this stage, at eight weeks, ensures the body systems are developed and from then on, the embryo is called the fetus.
(ROOT (S (NP (NP (DT The) (NN development)) (PP (IN of) (NP (NP (DT the) (JJ respiratory) (NN system)) (PP (IN in) (NP (DT the) (NN fetus)))))) (VP (VBZ begins) (PP (IN at) (NP (QP (RB about) (CD 4)) (NNS weeks)))) (. .)))
The development of the respiratory system in the fetus begins at about 4 weeks.