How would you write 0.0005 in scientific notation?

How many countries have portuguese as a national language?

Which area on the map would be most likely to have the most oil exploration in since the start of the 21st century? a) b) c) d) plz me

Why is the huronian supergroup rock formation particularly interesting to scientists? because it looks like a cross-section of a giant, stone encyclopedia because it formed during the period when oxygen began to accumulate in the atmosphere because it contains unusually large amounts of oxygen and sulfur because it dramatically altered the planet's development when it first formed