Read the following excerpt from a US court opinion:
```
dismissal is proper under 28 U.S.C. § 1404. Up until recently, “[t]he Fifth Circuit [had] declined to address the ‘enigmatic question of whether motions to dismiss on the basis of forum selection clauses are properly brought as motions under Fed.R.Civ.P. 12(b)(1) [or] 12(b)(3).’ ” Haynsworth v. The Corporation, 121 F.3d 956, 961 (5th Cir.1997). Most district courts in the Fifth Circuit followed the direction of Mitsui & Co. (USA), Inc. v. MIRA M/V, 111 F.3d 33 (5th Cir.1997), in which the Fifth Circuit, without commenting on the district court’s procedural choice, affirmed a district court’s granting of a Rule 12(b)(3) motion to dismiss for improper venue based on a forum selection clause See Ambraco, Inc. v. M/V CLIPPER FAITH, no. 06-9966, 2007 WL 1550960 at *1 (E.D.La., May 25, 2007) . Very recently, the Fifth Circuit shed some
```
What is the most suitable continuation to the opinion? Your options are:
A. recognizing circuit agreement that a motion to dismiss based on an arbitration clause is proper under rule 12b3
B. holding that a motion to dismiss based on a forumselection clause should be treated as a rule 12b3 motion to dismiss for improper venue
C. holding that a forumselection clause may be enforced under rule 12b3 as a motion to dismiss on the basis of improper venue
D. holding that since the fifth circuit has accepted rule 12b3 as a proper method for seeking dismissal for improper venue based on a forum selection clause the court need not decide whether a rule 12b1 motion  is appropriate
E. holding that when a forum selection clause designates  an arbitral forum  the proper remedy is dismissal
Reply with [A, B, C, D, E] only.