Questions

An up - selling is getting the customer to spend more money, buy a more expensive model of the same type of product, or add features or warranties that relate to the product viewed or purchased. 

A cross - sell is to get the customer to spend more money by adding more products from other categories than the product being viewed or purchased. 

Normal Gas welding use oxygen-acetylene.

Depending on what materials you are welding, there are some more options that might be used.

For example - MIG/TIG use Argon, MAG use an argon-something mix.

During convection, cool and dense air falls through the warmer and less dense air. The warm air having less mass is being displaced by the cooler which is much heavy. Convection always involves the air rising through the atmosphere.

The compound MgCl2 is named as Magnesium Chloride.

From the given data,

1 + 9 + 8 = 1

ONE + NINE + EIGHT

Consider the first letters and join them viz O N E = 1

So, now consider 2 + 8 + 9 in similar way

TWO+EIGHT+NINE

First letters are T E N = 10

2 + 8 + 9 = 1⃣0⃣