Question: Why in fact, did he not say that, since the Torah declares her Tamei mi'Safek, why would we think that she is permitted to eat T'rumah and to marry a Kohen?

Answer: If not for the Pesukim, we would have thought that she is only Tamei with regard to her husband, through whom she might be Chayvei Misas Beis-Din; whereas regarding T'rumah and Kehunah, we would have placed the woman on her Chezkas Kashrus.

Yerushalmi: However the Yerushalmi, in the first Perek (Halachah 2), on account of this Kashya, Darshens one of the three Pesukim with regard to the Yavam.

Yerushalmi (cont.): The Yersushalmi there, citing Rebbi Meir in a Beraisa, says as follows: 'There are three Tum'os mentioned in the Parshah, one for the husband, one for the adulterer and one for T'rumah.

Yerushalmi (cont.): Do we find such a thing as she being forbidden to her husband and permitted to eat T'rumah? Why not? If a bas Kohen who is married to a Yisrael is raped is she not permitted to her husband, yet she is forbidden to eat T'rumah (when her husband dies)?

Yerushalmi (cont.): (Nevertheless) we do not find a woman who is forbidden to her husband who is permitted to eat T'rumah.

Yerushalmi (concl.): Rebbi Avin said that from one is forced to say that one Pasuk is for the husband, one for the adulterer and one for the Yavam'.

Proof: Rebbi Yossi said, 'A Beraisa specifically says that - "If he dies, she performs Chalitzah but not Yibum'.

Refuted Question: One cannot ask how a Safek can be more stringent than a Vaday, because there where she Vaday committed adultery, she is permitted to eat T'rumah and to marry a Kohen ...

Source: Because in Perek Almanah (Yevamos, Daf 68.) we include from the Pasuk "u'Bas Kohen ki Sihyey le'Ish Zar" - that since she had relations with a man who is a stranger to her, he renders her Pasul, and we include a Ger Amoni and Mo'avi.

Source (cont.): And the Gemara asks there 'Perhaps we will include Chayvei K'risos too, seeing as they too are included in 'relations with someone who renders her Pasul. So why does the Tana not include them earlier?

Source (cont.): And the Gemara answers that the Torah writes "Ki Sih'yeh", with reference specifically to men on whom Kidushin take effect, to preclude Chayvei K'risos who are not subject to Kidushin.

Source (concl.): So we see that the Bi'ah of Chayvei K'risos does not disqualify her - and a married woman is included in Chayvei K'risos; So why will a Safek disqualify her?

Refutation: Rashi changes the text there. According to him, the text reads 'Perhaps "If she had relations" refers to Chayvei K'risus, but Chayvei La'avin, on whom Kidushin take effect, do not disqualify her. So how do we know that a Kuti, a Nasin and a Mamzer disqualify her?

Refutation (cont.): Those on whom Kidushin takes effect'. Since the Pasuk presents the Bi'ah with a Lashon of 'Havayah', we see that it is talking about those on whom Kidushin takes effect.

Refutation (cont.): We do not have the text 'To preclude Chayvei K'risus'.

Refutation (cont.): 'If so, a Nochri and an Eved ought not to disqualify either'? The Gemara could just as well have asked on Chayvei K'risus, only since it mentioned them earlier, when it said 'Kuti (alias a Nochri), and our Mishnah stated that an Eved disqualifies on account of Bi'ah'.

Refutation (cont.): And the Gemara answers - 'from the statement of Rebbi Yochanan ... '.

Refuted Explanation: There are some commentaries who explain 'Perhaps if she had relations with someone who is Pasul to her' with regard to Chayvei K'risus as well.

Refutation #1: But Rashi has many problems with that: Firstly, from the Mishnah in Arba'ah Achin (Ibid., Daf 33:) 'If they were Kohanos, they are Pasul from eating T'rumah because of the Isur of Eishes Ish'?

Refutation #2: Secondly, it is a Kal va'Chomer - If Chayvei La'avin disqualify, how much more so Chayvei K'risus?

Refutation #3: And thirdly, the Gemara says in Asarah Yuchsin (Kidushin, Daf 77:) 'A Kohen who has relations with his sister renders her a Zonah, in which case, the Bi'ah disqualifies her' ...

Source: As we learned in a Beraisa 'If a Leviyah who is captured or who had Bo'el a Be'ilas Z'nus, one may give her Ma'aser and she may eat it'. From which we extrapolate 'A Leviyah, yes, but T'rumah to a Kohenes, no'!? (See Mesores ha'Shas, 3).