Which is not a way to accelerate an object? a. speed it up c. change its direction b. slow it down d. apply balanced forces

Iknow the answer to 13 is b and 14 is d. i just need to know why the correct answers are correct

Can someone me with these questions plz.

If 34.2 grams of lithium react with excess water, how many liters of hydrogen gas can be produced at 299 kelvin and 1.21 atmospheres? 2 li (s) + 2 h2o (l) yields 2 lioh (aq) + h2 (g)