How has Apple been able to sustain its competitive advantage in the smartphone industry?A. by reducing its network effects B. by targeting its new products and services toward laggards C. by driving the price for the end user to zero d. by regularly introducing incremental improvements in its products

Ticker services began operations in 2015 and maintains long-term investments in available-for-sale securities. the year-end cost and fair values for its portfolio of these investments follow. portfolio of available-for-sale securities cost fair valuedecember 31, 2015 $ 369,060 $ 357,988 december 31, 2016 420,728 445,972 december 31, 2017 572,190 676,901 december 31, 2018 864,007 768,966 prepare journal entries to record each year-end fair value adjustment for these securities. calculation adjustment required to fair value adjustment.12/31/15 existing balance in fair value adjustment-afs (lt) required balance in fair value adjustment-afs (lt) adjustment required to fair value adjustment-afs (lt) 12/31/16 existing balance in fair value adjustment-afs (lt) required balance in fair value adjustment-afs (lt) adjustment required to fair value adjustment-afs (lt) 12/31/17 existing balance in fair value adjustment-afs (lt) required balance in fair value adjustment-afs (lt) adjustment required to fair value adjustment-afs (lt) 12/31/18 existing balance in fair value adjustment-afs (lt) required balance in fair value adjustment-afs (lt) adjustment required to fair value adjustment-afs (lt) record the year-end adjusting entry for the securities portfolio as of december 31, 2015.date general journal debit creditdec 31, 2015 record the year-end adjusting entry for the securities portfolio as of december 31, 2016.date general journal debit creditdec 31, 2016 record the year-end adjusting entry for the securities portfolio as of december 31, 2017.date general journal debit creditdec 31, 2017 record the year-end adjusting entry for the securities portfolio as of december 31, 2018.date general journal debit creditdec 31, 2018