The hyperconjugative stabilities of tert-butyl cation and `2`-butene, respectively, are due to
A. `sigmararrp` (empty) and `sigmararrpi^(**)` electron delocalizations
B. `sigmararrsigma^(**)` and `sigmararrpi` delectron delocalizations
C. `sigmararrp` (filled) and `sigmararrpi` electron delocalizations
D. p(fillled)`rarrsigma^(**)` and `sigma rarrpi^(**)` electron delocalizations
