Complementiser Phrase: The Case of English Wh-Embedded Clauses

English main-clause wh-questions form complementiser phrases with wh-words preposed to spec-C position. This is because English wh-words, as verb-complements originally, are strong enough to trigger wh-movement and auxiliary inversion. Persian EFL learners encounter an over-differentiation problem regarding the acquisition of auxiliary inversion rule in English standard questions. Once they have acquired the rule, the learners are very likely to overgeneralize it to English indirect or embedded questions. The present study aimed to discover Persian EFL learners' knowledge of wh-embedded clauses, specifically, when producing them orally. To this end, 48 Persian EFL learners at tertiary level took part as participants. An oral reproduction test of English wh-embedded clauses, a translation task, and a grammaticality judgment test containing wh-embedded clauses were used as instruments to collect data. The results revealed that the lower intermediate learners had problems in producing and reproducing correct wh-embedded clauses. Similarly, some problems were detected in the grammaticality judgment test. Difficulties were also observed with the intermediate and upper-intermediate learners. The major finding was obtained in the oral reproduction test where there was no significant difference among three proficiency groups of learners regarding the correct use of English wh-embedded clauses. The recent finding confirms the need for more work on Persian EFL learners' oral language production with an emphasis on wh-embedded clauses.