[Source or answer dispute] Official C: key suffix 50 vs named 30

What you will learn

Disputed-question explanation: official result first, then historical evidence, limitations and uncertainty.

Saved full original October 2021 exam text (local copy of CBP-authored PDF): cover instruction; Exam cover reference list: HTSUS edition; Exam category heading before questions 34-46; Question 45 stem opening as printed (exam PDF page 14; rendered temporarily and viewed); Question 45 stem: components (exam PDF page 14); Question 45 stem: operation (exam PDF page 14); Question 45 stem: comparison with a sphygmomanometer (exam PDF page 14); Question 45 choices A–E as printed (exam PDF page 14; rendered temporarily and viewed); Answer key row 45 as printed (key PDF page 2); Answer key page 2, row 45 (actual PNG viewed; text checked against key text); HTSUS 2020 heading 9018 article description (page 90-17); HTSUS 2020 electro-diagnostic group under 9018 (pages 90-17 and 90-18); HTSUS 2020 9018.19.55 (page 90-18); HTSUS 2020 9018.19.95 eight-digit line with rates (page 90-18); HTSUS 2020 9018.19.95 statistical suffix 30 (page 90-18); HTSUS 2020 9018.19.95 statistical suffix 35 (page 90-18); HTSUS 2020 9018.19.95 statistical suffix 50 (page 90-18); HTSUS 2020 page 90-18, 9018.19.95 suffixes 30/35/50/60 (actual PNG viewed; text checked against Chapter 90 PDF text); HTSUS 2020 9018.90.50 (choice D line, page 90-19); HTSUS 2020 9018.90.50 suffix 40 (choice D, page 90-19); HTSUS 2020 heading 9031 article description (choice E heading); HTSUS 2020 Chapter 90 note 1(m) (page 90-1) · October 21, 2021 Customs Broker License Examination, Category VIII – Classification (question 45 on exam PDF page 14, rendered temporarily and viewed); 'October 2021 Customs Broker License Exam Answer Key', row 45 on key page 2 (actual key-page2.png viewed). Cover reference: HTSUS 2020 Basic Edition, no supplements; Chapter 90 page 90-18 viewed as the actual 2020Basic90-18.png; Chapter 90 notes and 9018/9031 text read in the 2020 Basic Chapter 90 PDF text.
Explained using the historical edition for this exam.