You cannot go without a pencil when writing or drawing something. You have probably noticed letters H and B printed on your pencils．What，for example，do HB，2H or 3H mean?
Those are letters showing the hardness of the lead(铅)or graphite(石墨)in a pencil．H refers to hard lead．The bigger the Arabic number before the letter H，the harder the lead，and the lighter will be the colour. The hardest pencil has 6H on it．Such pencils are often used in making engineering drawings．People seldom write with them．B stands for soft lead．The bigger the number before the letter B，the softer the lead，and the darker will be the colour, the softest being the 6B pencil．Such pencils are favoured by artists．
The HB pencil has a lead core(中心部分)that is neither too soft nor too hard．Its colour is medium in its blackness．It is most suitable for ordinary(平常的)writing and drawing．
The number that goes before the letter H shows_________．

A．the model of the pencil

B．the factory where the pencil is made

C．how hard the pencil is

D．how long the pencil lasts

A4B pencil is _______ than a 3B one．

A．harder	B．softer
C．better	D．more expensive

According to the passage，an HB pencil is best for people like_________．

A．students	B．artists
C．printers	D．engineers