Read the following excerpt from a US court opinion:
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law, our review is de novo. See, e.g., State Police Ass’n of Mass. v. Comm’r, 125 F.3d 1, 3-4 (1st Cir.1997). Persons subject to the federal estate tax are required to file estate tax returns within fixed time parameters. I.R.C. § 6075. If such a person fails to file an estate tax return in a timeous manner, he has the burden of showing “that such failure is due to reasonable cause and not due to willful neglect.” Id. § 6651(a)(1). In the absence of such a showing, “there shall be added to the amount required to be shown as tax on such return” a late-filing penalty. Id. Imposition of this penalty is mandatory unless the failure to file on time was due to reasonable cause and not due to willful neglect. See Comm’r v. Lane-Wells Co., 321 U.S. 219, 224, 64 S.Ct. 511, 88 L.Ed. 684 (1944) ; Plunkett v. Comm’r, 118 F.2d 644, 649 (1st
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What is the most suitable continuation to the opinion? Your options are:
A. holding pennsylvanias similarly worded sixyear statute of limitations for paternity actions unconstitutional
B. holding defendant could not recover attorneys fees under predecessor to statute 38001 when defendant did not present contract claim
C. holding fees mandatory under predecessor statute of  38001
D. holding latefiling penalty mandatory absent reasonable cause under a similarly worded predecessor statute
E. holding that the statute is mandatory
Reply with [A, B, C, D, E] only.