( ( In addition ) ( , ( ( cigarette smoke ) ( also ( ( contains ( substances ( called ( ( carcinogens , ) ( which ( are ( responsible ( for ( causing ( ( certain types ) ( of cancer ) ) ) ) ) ) ) ) ) ) ) . ) ) ) ) )
(ROOT (S (PP (IN In) (NP (NN addition))) (, ,) (NP (NN cigarette) (NN smoke)) (ADVP (RB also)) (VP (VBZ contains) (SBAR (S (NP (NNS substances)) (VP (VBD called) (NP (NP (NNS carcinogens)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBP are) (ADJP (JJ responsible) (PP (IN for) (S (VP (VBG causing) (NP (NP (JJ certain) (NNS types)) (PP (IN of) (NP (NN cancer)))))))))))))))) (. .)))
In addition, cigarette smoke also contains substances called carcinogens, which are responsible for causing certain types of cancer.
(ROOT (S (NP (NNS Cigarettes)) (VP (VBP are) (NP (NP (DT a) (JJ major) (NN source)) (PP (IN of) (NP (NP (NNS carcinogens)) (, ,) (NP (NP (DT a) (NN kind)) (PP (IN of) (NP (NP (NN chemical) (NNS substances)) (VP (VBN linked) (PP (IN with) (NP (NN cancer))))))))))) (. .)))