OID for signatures

Perhaps someone could help me to undetand a3the meaning of RFC1423
section 4.3, specifically:

"This section identifies the alternative algoritms which shall be used"
and "Only one alternative is..."

my understanding of the word "alternative" means that there are at least
two.  Does this mean that the algorithm from X.509 {joint-iso-ccitt
ds(5) modules(1) algorithmObjectIdentifiers(8) 3} is allowed?

Peace ..Tom Jones