请问将研发成本费用化处理的a1理由是：

1. determiningtheactivitiestobeincludedaspartofresearchanddevelopmentisasubjectiveprocess.
   确定一种活动是否为研发行为是一个主观的判断

2. thebenefitsderivedfromresearchanddevelopmenteffortsmaylaterbesoldtoothersoutsideofthecompany.
   来源于研发活动的益处后来可能会被出售给公司以外的其他人

3. itisdifficulttodetermineiftheassetsusedforresearchanddevelopmentwillhavealternativefutureuses.
   很难确定被用作研发的资产将来是否另有用处

4. themagnitudeandtimingofthefuturebenefitsreceivedfromresearchanddevelopmentcostsaredifficulttodetermine.
   很难确定从研发活动中获取多少益处以及何时获益

答案：D