121 b4 好像不相干啊
(4)Special rule for certain sales by surviving spouses
In the case of a sale or exchange of property by an unmarried individual whose spouse is deceased on the date of such sale, paragraph (1) shall be applied by substituting “$500,000” for “$250,000” if such sale occurs not later than 2 years after the date of death of such spouse and the requirements of paragraph (2)(A) were met immediately before such date of death
121 d （10） 倒是说了，但说的是要持有5年，不知道理解得对不对
(d)Special rules
(10)Property acquired in like-kind exchange
If a taxpayer acquires property in an exchange with respect to which gain is not recognized (in whole or in part) to the taxpayer under subsection (a) or (b) of section 1031, subsection (a) shall not apply to the sale or exchange of such property by such taxpayer (or by any person whose basis in such property is determined, in whole or in part, by reference to the basis in the hands of such taxpayer) during the 5-year period beginning with the date of such acquisition.
