Check all the true statements about sound and light waves.
Light waves may travel either through a transparent medium or through empty space.
Sound waves travel through all substances.
Light waves are absorbed and reflected by opaque materials so that no light travels through them.
Light waves cannot travel through empty space.
Sound waves do not require a medium for traveling,
Sound waves can only travel through transparent objects
Sound waves require a medium for traveling,

See explanation.

Explanation:

Let us go through each of statements one by one.

Light waves may travel either through a transparent medium or through empty space.

Yes, light travels through empty space as well as through transparent media, however, in the latter its speed is slowed down.

Sound waves travel through all substances.

Sound waves are vibrations in a medium. All substances  can vibrate; therefore, sound travels through all substances.

Light waves are absorbed and reflected by opaque materials so that no light travels through them.

This is true. The reason light does not pass through an opaque substance is because it is absorbed or reflected way from us.

Light waves cannot travel through empty space.

No, electromagnetic radiation can travel through empty space because it is  not a disturbance in a medium.

Sound waves do not require a medium for traveling,

Nope. Sound waves are disturbances in a medium—they cannot exist independent; therefore, they require a medium for travelling.

Sound waves can only travel through transparent objects

No. Sound waves travel through all substances that can vibrate.

Sound waves require a medium for traveling,

As sound waves are vibrations in a medium, they need medium in which they can exist and travel.

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explanation:

  the grams     of oxygen gas   that can be produced     is 20.6   grams of o₂

calculation

2liclo₃ →   2 licl + 3 o₂

step 1:   find the moles of liclo₃

moles = mass÷ molar mass

from periodic table the molar mass of liclo₃ =6.9 +35.5   +(16 x3) =90.4 g/mol

moles=38.7 g÷90.4 g/mol=0.4281   moles

step 2:   use the   mole ratio   to calculate the moles of o2

from equation above, liclo₃: o₂   is 2: 3  

therefore the moles of   o₂=0.4281 moles x3/2 =0.6422   moles

step 3: find mass   of o₂

mass= moles x molar mass

from periodic table the   molar mass of   o₂ = 16 x2= 32 g/mol

mass=0.6422   moles   x   32 g/mol = 20.6 grams of o₂