Which of the following sets of characteristics would best describe an ARMA(3,3) process:
Select one:
a. A slowly decaying ACF and PACF
b. None of these
c. A slowly decaying ACF, and a PACF with 3 significant spikes
d. A slowly decaying PACF and an ACF with 3 significant spikes
e. An ACF and a PACF with 3 significant spikes