Express 0.00045 in scientific notation. A 4.5 × 10⁻³ B 4.5 × 10⁻⁴ C 45 × 10⁻⁵ D 0.45 × 10⁻³ ✓ Correct Answer: Option B 0.00045 = 4.5 × 10⁻⁴ (decimal moves 4 places right). Practice ACT Exam Prep Quizzes → Browse All Questions Study Flashcards