题目

Samsung says new Galaxy Note 7 smartphones will be available in U.S. stores starting Wednesday to replace about 1 million devices that are being recalled because their batteries can catch fire. The South Korean company has been scrambling to fix problems caused by faulty batteries in the latest version of its top of the line smartphone, which first went on sale last month. When it first offered on Sept. 2 to replace the affected Note 7 phones, Samsung said it would swap them for models of its other phones, such as the Galaxy S7, until supplies of replacement Note 7 devices became avail设是虚数单位，则复数的虚部为（ ）A.4 B.4 C.-4 D.-4