L-Type Calcium Channels, Such as Those Found in the Soma

L-type calcium channels, such as those found in the soma of leech Retzius neurons, are especially suitable for extrasynaptic signaling because they

A) open only after a lag of up to one second.
B) have a very high depolarization threshold for opening.
C) are permeable to magnesium as well as calcium.
D) inactivate rapidly after opening.
E) are not easily inactivated.