b) using "how"

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How Long? How many? How much? How much time? 
source: Learn English with Emma [engVid]        2016年6月15日
quiz: http://www.engvid.com/how-to-ask-ques...
Conversation Patterns: How Much / How Many
source: labonteesl

Questions with How Much and How Many
source: MadridTeacher

How often ...? + always, usually, often, sometimes, never
source: AlexESLvid

How often...?
source: learnamericanenglish

"How often do you...?" Everyday activities and frequency
(English Conversation Practice)
source: Mark Kulek

HOW OFTEN? (+ adverbs of frequency)
source: English Lessons

How long...? (present perfect continuous)
source: English Lessons

Answering "how long" questions with "since" and "for" (with the Present Perfect)
source: AlexESLvid 

How long-does it take? 
source: Real English® 

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