There are questions about Josh Allen’s accuracy, Josh Rosen’s personality, Sam Darnold’s turnovers and Baker Mayfield’s height. The nice news for the 49ers: They don’t have to figure out the answers surrounding the top quarterbacks in this year’s NFL draft. The 49ers have Jimmy Garoppolo signed through 2022, but their investigative work this week at the NFL combine in Indianapolis will indirectly involve the QB position. For example, there is the matter of supporting their $137.5 million investment by fortifying their offensive line and wide receiver corps. Then, there is the issue of stifling their opponents’ QBs: The 49ers have glaring needs for cornerbacks and pass-rushers. On Feb. 9, the day after signing Garoppolo to his five-year deal, general manager John Lynch said the 49ers had secured a “big piece” while noting the heavy lifting that remained. “We were 6-10, OK?” Lynch said. “So this is a big day for us, but we have a long way to go. And we're fully aware of that.” The 49ers have used six of their past seven first-round picks on defensive players, and that trend could continue in 2018. At cornerback, the cupboard is largely bare beyond starter Ahkello Witherspoon, a 2017 third-round pick who had a strong rookie season, and slot cornerback K’Waun Williams, who received a midseason contract extension.