In nominative–accusative, only arguments S and A can be omitted and not argument O.  English The omitted subject argument of the embedded clause must correspond to the subject (nominative) of the matrix-clause. If it corresponds to the object (accusative), the sentence is ungrammatical. If English were an ergative–absolutive language, one would expect to see: Here the omitted argument of the embedded clause corresponds to the direct object (absolutive) of the matrix-clause. If it corresponds to the subject (ergative), the sentence is ungrammatical. The alignment system also impacts the triggering and realization of other such syntactic processes as raising constructions, subject-controlled subject deletion and object-controlled subject deletion. Languages exhibiting accusative alignment are the most widespread of all of the alignment types. These languages can be found on every continent, in comparison to languages with ergative alignment that are restricted to certain areas of the world, namely the Caucasus, parts of North American and Mesoamerica, the Tibetan plateau, and Australia. The map shows the distribution of languages with the various alignment types, and the following list gives a short sampling of accusative languages and their distribution across the globe:   One of the ways in which the production of a nominative–accusative case marking system can be explained is from an Optimality Theoretic perspective. Case marking is said to fulfill two functions, or constraints: an identifying function and a distinguishing function. The identifying function is exemplified when case morphology encodes (identifies) specific semantic, thematic, or pragmatic properties or information about the nominal argument. Accusative case in the position of the direct object, for example, can be a strong identifier of patienthood. The distinguishing function is used to distinguish between the core arguments, the subject and the object, of a transitive clause. Helen de Hoop and Andrej Malchukov explain the motivation and need for the distinguishing function in "Case marking strategies":  It is rare for case to serve only the distinguishing function, which overlaps greatly with the ‘identify’ function. Other ways of disambiguating the arguments of a transitive predicate (subject agreement, word order restriction, context, intonation, etc.) may explain this cross-linguistic observation. De Hoop and Malchukov argue that case systems that are completely based on the identification function must be richer in case morphology compared to languages based mainly on the distinguishing function.