zone business), and (C) during substantially all of the taxpayer's holding period for such interest, such partnership qualified as a qualified gigabit opportunity zone business. (4) Qualified gigabit opportunity zone business property (A) In general The term qualified gigabit opportunity zone business property means tangible property used in a trade or business of the taxpayer if— (i) such property— (I) is used primarily to provide broadband transmission services to locations which do not have such service that meets the minimum speed requirements required for universal service support under Phase II of the Connect America Fund of the Federal Communications Commission, as set forth under subpart D of part 54 of title 47, Code of Federal Regulations, and (II) is capable of transmitting signals at a rate of at least 1,000,000,000 bits per second, (ii) such property was acquired by the taxpayer by purchase (as defined in section 179(d)(2)) after December 31, 2017, (iii) the original use of such property in the qualified gigabit opportunity zone commences with the taxpayer or the taxpayer substantially improves the property, and (iv) during substantially all of the taxpayer’s holding period for such property, substantially all of the use of such property was in a qualified gigabit opportunity zone. (B) Special rule for certain property In the case of property which is placed in service before January 1, 2021, and which is with respect to technology described in paragraph (4) or (5) of subsection (c), subparagraph (A)(i)(II) shall be applied by substituting 150,000,000 bits per second for 1,000,000,000 bits per second . (C) Substantial improvement For purposes of subparagraph (A)(iii), property shall be treated as substantially improved by the taxpayer only if, during any 30-month period beginning after the date of acquisition of such property, additions to basis with respect to such property in the hands of the taxpayer exceed an amount equal to the adjusted basis of such property at the beginning of such 30-month