QUES: His theory of light predicted that the velocity of light should decrease as it passes into a denser medium

correct the punctuation.

CORRECTED: His theory of light predicted that the velocity of light should decrease as it passes into a denser medium.

QUES: Before you can open a DST file youll need to figure out what kind of file the DST file extension refers to

correct the punctuation.

CORRECTED: Before you can open a DST file, you'll need to figure out what kind of file the DST file extension refers to.

QUES: Collected cleaned and then sliced Fresh or included in traditional high quality recipes taste their overwhelming flavour in a dish of tagliolini on a nice cut of meat or in a sauce on a piece of nicely toasted bread

correct the punctuation.

CORRECTED:
Collected, cleaned and then sliced? Fresh or included in traditional high quality recipes, taste their overwhelming flavour in a dish of tagliolini, on a nice cut of meat or in a sauce on a piece of nicely toasted bread!